15.1. os — Interfaces diversas para o sistema operacional

Este módulo provê uma maneira portátil de usar funcionalidades dependentes de sistema operacional. Se você só quer ler ou escrever um arquivo, veja open(); se você quer manipular estruturas de diretórios, veja o módulo os.path; e se você quer ler todas as linhas de todos os arquivos na linha de comando, veja o módulo fileinput. Para criar arquivos e diretórios temporários, veja o módulo tempfile; e para manipulação em alto nível de arquivos e diretórios, veja o módulo shutil.

Notas sobre a disponibilidade dessas funções:

  • O modelo dos módulos dependentes do sistema operacional embutidos no Python é tal que, desde que a mesma funcionalidade esteja disponível, a mesma interface é usada; por exemplo, a função os.stat(path) retorna informações estatísticas sobre path no mesmo formato (que é originado com a interface POSIX).

  • Extensões específicas a um sistema operacional também estão disponíveis através do módulo: mod:os, mas usá-las é, naturalmente, uma ameaça à portabilidade.

  • Uma nota “Disponibilidade: Unix” significa que essa função é comumente encontrada em sistemas Unix. Não faz nenhuma reivindicação sobre sua existência em um sistema operacional específico.

  • <br>

Nota

Todas as funções nesse módulo levantam a exceção OSError, no caso de nomes e caminhos de arquivos inválidos ou inacessíveis, ou no caso de outros argumentos que possuem o tipo correto, mas não são aceitos pelo sistema operacional.

exception os.error

Um nome alternativo para a exceção built-in OSError.

os.name

The name of the operating system dependent module imported. The following names have currently been registered: 'posix', 'nt', 'os2', 'ce', 'java', 'riscos'.

Ver também

sys.platform tem uma granularidade mais fina. os.uname() fornece informação de versões dependentes do sistema.

O módulo platform provê verificações detalhadas sobre a identificação do sistema.

15.1.1. Parâmetros do Processo

Essas funções e itens de dados fornecem informações e operam no processo atual e no usuário.

os.environ

Um objeto mapping representando uma string do ambiente. Por exemplo, environ['HOME'] é o nome do caminho do seu diretório pessoal (em algumas plataformas), e é equivalente a getenv("HOME") em C.

Este mapeamento é capturado na primeira vez que o módulo os é importado, normalmente durante a inicialização do Python, como parte do processamento do arquivo site.py. Mudanças no ambiente feitas após esse momento não são refletidas em os.environ, exceto pelas mudanças feitas modificando os.environ diretamente.

Se a plataforma suportar a função putenv(), esse mapeamento pode ser usado para modificar o ambiente, além de consultá-lo. putenv() será chamado automaticamente quando o mapeamento for modificado.

Nota

Chamar a função putenv() diretamente não muda os.environ, por isso é melhor modificar os.environ.

Nota

Em algumas plataformas, incluindo FreeBSD e Mac OS X, a modificação de environ pode causar vazamentos de memória. Consulte a documentação do sistema para putenv().

Se a função putenv() não for fornecida, uma cópia modificada desse mapeamento pode ser passada para as funções apropriadas de criação de processos, para fazer com que os processos filhos usem um ambiente modificado.

Se a plataforma suportar a função unsetenv(), os itens nesse mapeamento poderão ser excluídos para remover variáveis de ambiente. unsetenv() será chamado automaticamente quando um item é excluído de os.environ, e quando um dos métodos pop() ou clear() é chamado.

Alterado na versão 2.6: Also unset environment variables when calling os.environ.clear() and os.environ.pop().

os.chdir(path)
os.fchdir(fd)
os.getcwd()

Essas funções são descritas em: Arquivos e Diretórios.

os.ctermid()

Retorna o nome do arquivo correspondente ao terminal de controle do processo.

Disponibilidade: Unix.

os.getegid()

Retorna o efetivo ID do grupo do processo atual. Isso corresponde ao bit “set id” no arquivo que está sendo executado no processo atual.

Disponibilidade: Unix.

os.geteuid()

Retorna o efetivo ID de usuário do processo atual.

Disponibilidade: Unix.

os.getgid()

Retorna o ID real do grupo do processo atual.

Disponibilidade: Unix.

os.getgroups()

Retorna a lista de IDs de grupos suplementares associados ao processo atual.

Disponibilidade: Unix.

Nota

No Mac OS X, o comportamento da função getgroups() difere um pouco de outras plataformas Unix. Se o interpretador Python foi compilado para distribuição na versão 10.5 ou anterior, getgroups() retorna a lista de ids de grupos efetivos, associados ao processo de usuário atual; esta lista é limitada a um número de entradas definido pelo sistema, tipicamente 16, e pode ser modificada por chamadas para setgroups() se tiver o privilégio adequado. Se foi compilado para distribuição na versão maior que 10.5, getgroups() retorna a lista de acesso de grupo atual para o usuário associado ao id de usuário efetivo do processo; a lista de acesso de grupo pode mudar durante a vida útil do processo, e ela não é afetada por chamadas para setgroups(), e seu comprimento não é limitado a 16. O valor da constante MACOSX_DEPLOYMENT_TARGET, pode ser obtido com sysconfig.get_config_var().

os.initgroups(username, gid)

Chama o initgroups() do sistema para inicializar a lista de acesso ao grupo com todos os grupos dos quais o nome de usuário especificado é membro, mais o ID do grupo especificado.

Disponibilidade: Unix.

Novo na versão 2.7.

os.getlogin()

Return the name of the user logged in on the controlling terminal of the process. For most purposes, it is more useful to use the environment variable LOGNAME to find out who the user is, or pwd.getpwuid(os.getuid())[0] to get the login name of the process’s real user id.

Disponibilidade: Unix.

os.getpgid(pid)

Retorna o ID do grupo de processo com pid. Se pid for 0, o ID do grupo do processo atual é retornado.

Disponibilidade: Unix.

Novo na versão 2.3.

os.getpgrp()

Retorna o ID do grupo de processo atual.

Disponibilidade: Unix.

os.getpid()

Retorna o id do processo atual.

Disponibilidade: Unix, Windows.

os.getppid()

Return the parent’s process id.

Disponibilidade: Unix.

os.getresuid()

Retorna uma tupla (ruid, euid, suid) indicando os IDs de usuário reais, efetivos e salvos do processo atual.

Disponibilidade: Unix.

Novo na versão 2.7.

os.getresgid()

Retorna uma tupla (rgid, egid, sgid) indicando os IDs de grupo reais, efetivos e salvos do processo atual.

Disponibilidade: Unix.

Novo na versão 2.7.

os.getuid()

Retorna o ID de usuário real do processo atual.

Disponibilidade: Unix.

os.getenv(varname[, value])

Return the value of the environment variable varname if it exists, or value if it doesn’t. value defaults to None.

Disponibilidade: a maioria dos sabores de Unix, Windows.

os.putenv(varname, value)

Set the environment variable named varname to the string value. Such changes to the environment affect subprocesses started with os.system(), popen() or fork() and execv().

Disponibilidade: a maioria dos sabores de Unix, Windows.

Nota

Em algumas plataformas, incluindo FreeBSD e Mac OS X, a configuração environ pode causar vazamento de memória. Consulte a documentação do sistema para putenv.

Quando há suporte a putenv(), as atribuições para itens em os.environ são automaticamente convertidas em chamadas correspondentes para putenv(); no entanto, chamadas para putenv() não atualiza os.environ, então é realmente preferível atribuir itens a os.environ.

os.setegid(egid)

Define o ID do grupo efetivo do processo atual.

Disponibilidade: Unix.

os.seteuid(euid)

Define o ID de usuário efetivo do processo atual.

Disponibilidade: Unix.

os.setgid(gid)

Define o ID do grupo do processo atual.

Disponibilidade: Unix.

os.setgroups(groups)

Define a lista de IDs de grupo suplementares associados ao processo atual como groups. groups deve ser uma sequência e cada elemento deve ser um número inteiro identificando um grupo. Esta operação normalmente está disponível apenas para o superusuário.

Disponibilidade: Unix.

Novo na versão 2.2.

Nota

No Mac OS X, o tamanho de groups não pode exceder o número máximo definido pelo sistema de IDs de grupo efetivos, normalmente 16. Consulte a documentação de getgroups() para casos em que ele pode não retornar o mesmo conjunto de listas de grupos chamando setgroups().

os.setpgrp()

Executa a chamada de sistema setpgrp() ou setpgrp (0, 0) dependendo da versão implementada (se houver). Veja o manual do Unix para a semântica.

Disponibilidade: Unix.

os.setpgid(pid, pgrp)

Faz a chamada de sistema setpgid() para definir o ID do grupo do processo com pid para o grupo de processos com o id pgrp. Veja o manual do Unix para a semântica.

Disponibilidade: Unix.

os.setregid(rgid, egid)

Define os IDs de grupo real e efetivo do processo atual

Disponibilidade: Unix.

os.setresgid(rgid, egid, sgid)

Define os IDs de grupo real, efetivo e salvo do processo atual

Disponibilidade: Unix.

Novo na versão 2.7.

os.setresuid(ruid, euid, suid)

Define os IDs de usuário real, efetivo e salvo do processo atual

Disponibilidade: Unix.

Novo na versão 2.7.

os.setreuid(ruid, euid)

Define os IDs de usuário real e efetivo do processo atual.

Disponibilidade: Unix.

os.getsid(pid)

Executa a chamada de sistema getsid(). Veja o manual do Unix para semântica.

Disponibilidade: Unix.

Novo na versão 2.4.

os.setsid()

Executa a chamada de sistema setsid(). Veja o manual do Unix para semântica.

Disponibilidade: Unix.

os.setuid(uid)

Define o ID de usuário do processo atual.

Disponibilidade: Unix.

os.strerror(code)

Retorna a mensagem de erro correspondente ao código de erro em code. Nas plataformas em que strerror() retorna NULL quando recebe um número de erro desconhecido, ValueError é gerada.

Disponibilidade: Unix, Windows.

os.umask(mask)

Define o umask numérico atual e retorna o umask anterior.

Disponibilidade: Unix, Windows.

os.uname()

Return a 5-tuple containing information identifying the current operating system. The tuple contains 5 strings: (sysname, nodename, release, version, machine). Some systems truncate the nodename to 8 characters or to the leading component; a better way to get the hostname is socket.gethostname() or even socket.gethostbyaddr(socket.gethostname()).

Disponibilidade: distribuicões recentes de Unix

os.unsetenv(varname)

Unset (delete) the environment variable named varname. Such changes to the environment affect subprocesses started with os.system(), popen() or fork() and execv().

Quando unsetenv() é suportado, a exclusão de itens em os.environ é automaticamente traduzida para uma chamada correspondente a unsetenv(); no entanto, chamadas a unsetenv() não atualizam os.environ, por isso, na verdade é preferível excluir itens de os.environ.

Disponibilidade: a maioria dos sabores de Unix, Windows.

15.1.2. Criação de Objetos Files

These functions create new file objects. (See also open().)

os.fdopen(fd[, mode[, bufsize]])

Return an open file object connected to the file descriptor fd. The mode and bufsize arguments have the same meaning as the corresponding arguments to the built-in open() function. If fdopen() raises an exception, it leaves fd untouched (unclosed).

Disponibilidade: Unix, Windows.

Alterado na versão 2.3: When specified, the mode argument must now start with one of the letters 'r', 'w', or 'a', otherwise a ValueError is raised.

Alterado na versão 2.5: On Unix, when the mode argument starts with 'a', the O_APPEND flag is set on the file descriptor (which the fdopen() implementation already does on most platforms).

os.popen(command[, mode[, bufsize]])

Open a pipe to or from command. The return value is an open file object connected to the pipe, which can be read or written depending on whether mode is 'r' (default) or 'w'. The bufsize argument has the same meaning as the corresponding argument to the built-in open() function. The exit status of the command (encoded in the format specified for wait()) is available as the return value of the close() method of the file object, except that when the exit status is zero (termination without errors), None is returned.

Disponibilidade: Unix, Windows.

Obsoleto desde a versão 2.6: This function is obsolete. Use the subprocess module. Check especially the Replacing Older Functions with the subprocess Module section.

Alterado na versão 2.0: This function worked unreliably under Windows in earlier versions of Python. This was due to the use of the _popen() function from the libraries provided with Windows. Newer versions of Python do not use the broken implementation from the Windows libraries.

os.tmpfile()

Return a new file object opened in update mode (w+b). The file has no directory entries associated with it and will be automatically deleted once there are no file descriptors for the file.

Disponibilidade: Unix, Windows.

There are a number of different popen*() functions that provide slightly different ways to create subprocesses.

Obsoleto desde a versão 2.6: All of the popen*() functions are obsolete. Use the subprocess module.

For each of the popen*() variants, if bufsize is specified, it specifies the buffer size for the I/O pipes. mode, if provided, should be the string 'b' or 't'; on Windows this is needed to determine whether the file objects should be opened in binary or text mode. The default value for mode is 't'.

Also, for each of these variants, on Unix, cmd may be a sequence, in which case arguments will be passed directly to the program without shell intervention (as with os.spawnv()). If cmd is a string it will be passed to the shell (as with os.system()).

These methods do not make it possible to retrieve the exit status from the child processes. The only way to control the input and output streams and also retrieve the return codes is to use the subprocess module; these are only available on Unix.

For a discussion of possible deadlock conditions related to the use of these functions, see Flow Control Issues.

os.popen2(cmd[, mode[, bufsize]])

Execute cmd as a sub-process and return the file objects (child_stdin, child_stdout).

Obsoleto desde a versão 2.6: This function is obsolete. Use the subprocess module. Check especially the Replacing Older Functions with the subprocess Module section.

Disponibilidade: Unix, Windows.

Novo na versão 2.0.

os.popen3(cmd[, mode[, bufsize]])

Execute cmd as a sub-process and return the file objects (child_stdin, child_stdout, child_stderr).

Obsoleto desde a versão 2.6: This function is obsolete. Use the subprocess module. Check especially the Replacing Older Functions with the subprocess Module section.

Disponibilidade: Unix, Windows.

Novo na versão 2.0.

os.popen4(cmd[, mode[, bufsize]])

Execute cmd as a sub-process and return the file objects (child_stdin, child_stdout_and_stderr).

Obsoleto desde a versão 2.6: This function is obsolete. Use the subprocess module. Check especially the Replacing Older Functions with the subprocess Module section.

Disponibilidade: Unix, Windows.

Novo na versão 2.0.

(Note that child_stdin, child_stdout, and child_stderr are named from the point of view of the child process, so child_stdin is the child’s standard input.)

This functionality is also available in the popen2 module using functions of the same names, but the return values of those functions have a different order.

15.1.3. Operações dos Descritores de Arquivos

Estas funções operam em fluxos de E/S referenciados usando descritores de arquivos.

Descritores de arquivos são pequenos números inteiros correspondentes a um arquivo que foi aberto pelo processo atual. Por exemplo, a entrada padrão geralmente é o descritor de arquivo 0, a saída padrão 1 e erro padrão 2. Outros arquivos abertos por um processo serão então atribuídos 3, 4, 5, e assim por diante. O nome “descritor de arquivo” é um pouco enganoso; em plataformas UNIX, sockets e pipes também são referenciados como descritores de arquivos.

The fileno() method can be used to obtain the file descriptor associated with a file object when required. Note that using the file descriptor directly will bypass the file object methods, ignoring aspects such as internal buffering of data.

os.close(fd)

Fecha o descritor de arquivo * fd *.

Disponibilidade: Unix, Windows.

Nota

Esta função destina-se a E/S de baixo nível e deve ser aplicada a um descritor de arquivo retornado por os.open() ou pipe(). Para fechar um “objeto arquivo” retornado pela função embutida open() ou by popen() ou fdopen(), use seu método close().

os.closerange(fd_low, fd_high)

Close all file descriptors from fd_low (inclusive) to fd_high (exclusive), ignoring errors. Equivalent to:

for fd in xrange(fd_low, fd_high):
    try:
        os.close(fd)
    except OSError:
        pass

Disponibilidade: Unix, Windows.

Novo na versão 2.6.

os.dup(fd)

Return a duplicate of file descriptor fd.

Disponibilidade: Unix, Windows.

os.dup2(fd, fd2)

Duplicate file descriptor fd to fd2, closing the latter first if necessary.

Disponibilidade: Unix, Windows.

os.fchmod(fd, mode)

Change the mode of the file given by fd to the numeric mode. See the docs for chmod() for possible values of mode.

Disponibilidade: Unix.

Novo na versão 2.6.

os.fchown(fd, uid, gid)

Change the owner and group id of the file given by fd to the numeric uid and gid. To leave one of the ids unchanged, set it to -1.

Disponibilidade: Unix.

Novo na versão 2.6.

os.fdatasync(fd)

Força de gravação de arquivo com descritor de arquivo fd no disco. Não força a atualização de metadados.

Disponibilidade: Unix.

Nota

Esta função não está disponível no MacOS.

os.fpathconf(fd, name)

Retorna informações de configuração de sistema relevantes para um arquivo aberto. name especifica o valor de configuração para recuperar; pode ser uma string que é o nome de um valor do sistema definido; estes nomes são especificados em uma série de padrões (POSIX.1, Unix 95, Unix 98 e outros). Algumas plataformas definem nomes adicionais também. Os nomes conhecidos do sistema operacional hospedeiro são dadas no dicionário pathconf_names. Para variáveis ​​de configuração não incluídas neste mapeamento, também é aceito passar um número inteiro para name.

Se name for uma string e não for conhecida, ValueError é gerado. Se um valor específico para name não for compatível com o sistema de host, mesmo que seja incluído no pathconf_names, um erro OSError é gerado com errno.EINVAL como número do erro.

Disponibilidade: Unix.

os.fstat(fd)

Return status for file descriptor fd, like stat().

Disponibilidade: Unix, Windows.

os.fstatvfs(fd)

Return information about the filesystem containing the file associated with file descriptor fd, like statvfs().

Disponibilidade: Unix.

os.fsync(fd)

Gravação à força no disco de arquivo com descritor de arquivo fd. No Unix, isto chama a função nativa fsync(); no Windows, a função de MS _commit().

If you’re starting with a Python file object f, first do f.flush(), and then do os.fsync(f.fileno()), to ensure that all internal buffers associated with f are written to disk.

Availability: Unix, and Windows starting in 2.2.3.

os.ftruncate(fd, length)

Truncate the file corresponding to file descriptor fd, so that it is at most length bytes in size.

Disponibilidade: Unix.

os.isatty(fd)

Retorna True se o descritor de arquivo fd estiver aberto e conectado a um dispositivo do tipo tty, senão False.

os.lseek(fd, pos, how)

Define a posição atual do descritor de arquivo fd para a posição pos, modificada por how: SEEK_SET ou 0 para definir a posição em relação ao início do arquivo; SEEK_CUR ou 1 para defini-la em relação à posição atual; SEEK_END ou 2 para defini-la em relação ao final do arquivo. Retorna a nova posição do cursor em bytes, a partir do início.

Disponibilidade: Unix, Windows.

os.SEEK_SET
os.SEEK_CUR
os.SEEK_END

Parâmetros para a function lseek(). Seus valores são respectivamente 0, 1, e 2.

Availability: Windows, Unix.

Novo na versão 2.5.

os.open(file, flags[, mode])

Open the file file and set various flags according to flags and possibly its mode according to mode. The default mode is 0777 (octal), and the current umask value is first masked out. Return the file descriptor for the newly opened file.

For a description of the flag and mode values, see the C run-time documentation; flag constants (like O_RDONLY and O_WRONLY) are defined in this module too (see open() flag constants). In particular, on Windows adding O_BINARY is needed to open files in binary mode.

Disponibilidade: Unix, Windows.

Nota

This function is intended for low-level I/O. For normal usage, use the built-in function open(), which returns a “file object” with read() and write() methods (and many more). To wrap a file descriptor in a “file object”, use fdopen().

os.openpty()

Open a new pseudo-terminal pair. Return a pair of file descriptors (master, slave) for the pty and the tty, respectively. For a (slightly) more portable approach, use the pty module.

Disponibilidade: alguns sabores de Unix

os.pipe()

Create a pipe. Return a pair of file descriptors (r, w) usable for reading and writing, respectively.

Disponibilidade: Unix, Windows.

os.read(fd, n)

Read at most n bytes from file descriptor fd. Return a string containing the bytes read. If the end of the file referred to by fd has been reached, an empty string is returned.

Disponibilidade: Unix, Windows.

Nota

This function is intended for low-level I/O and must be applied to a file descriptor as returned by os.open() or pipe(). To read a “file object” returned by the built-in function open() or by popen() or fdopen(), or sys.stdin, use its read() or readline() methods.

os.tcgetpgrp(fd)

Return the process group associated with the terminal given by fd (an open file descriptor as returned by os.open()).

Disponibilidade: Unix.

os.tcsetpgrp(fd, pg)

Set the process group associated with the terminal given by fd (an open file descriptor as returned by os.open()) to pg.

Disponibilidade: Unix.

os.ttyname(fd)

Return a string which specifies the terminal device associated with file descriptor fd. If fd is not associated with a terminal device, an exception is raised.

Disponibilidade: Unix.

os.write(fd, str)

Write the string str to file descriptor fd. Return the number of bytes actually written.

Disponibilidade: Unix, Windows.

Nota

This function is intended for low-level I/O and must be applied to a file descriptor as returned by os.open() or pipe(). To write a “file object” returned by the built-in function open() or by popen() or fdopen(), or sys.stdout or sys.stderr, use its write() method.

15.1.3.1. open() flag constants

The following constants are options for the flags parameter to the open() function. They can be combined using the bitwise OR operator |. Some of them are not available on all platforms. For descriptions of their availability and use, consult the open(2) manual page on Unix or the MSDN on Windows.

os.O_RDONLY
os.O_WRONLY
os.O_RDWR
os.O_APPEND
os.O_CREAT
os.O_EXCL
os.O_TRUNC

As constantes acima estão disponíveis no Unix e Windows.

os.O_DSYNC
os.O_RSYNC
os.O_SYNC
os.O_NDELAY
os.O_NONBLOCK
os.O_NOCTTY

As constantes acima estão disponíveis apenas no Unix.

os.O_BINARY
os.O_NOINHERIT
os.O_SHORT_LIVED
os.O_TEMPORARY
os.O_RANDOM
os.O_SEQUENTIAL
os.O_TEXT

As constantes acima estão disponíveis apenas no Windows.

os.O_ASYNC
os.O_DIRECT
os.O_DIRECTORY
os.O_NOFOLLOW
os.O_NOATIME
os.O_SHLOCK
os.O_EXLOCK

As constantes acima são extensões e não estarão presentes, se não forem definidos pela biblioteca C.

15.1.4. Arquivos e Diretórios

os.access(path, mode)

Use the real uid/gid to test for access to path. Note that most operations will use the effective uid/gid, therefore this routine can be used in a suid/sgid environment to test if the invoking user has the specified access to path. mode should be F_OK to test the existence of path, or it can be the inclusive OR of one or more of R_OK, W_OK, and X_OK to test permissions. Return True if access is allowed, False if not. See the Unix man page access(2) for more information.

Disponibilidade: Unix, Windows.

Nota

Using access() to check if a user is authorized to e.g. open a file before actually doing so using open() creates a security hole, because the user might exploit the short time interval between checking and opening the file to manipulate it. It’s preferable to use EAFP techniques. For example:

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

É melhor escrito como:

try:
    fp = open("myfile")
except IOError as e:
    if e.errno == errno.EACCES:
        return "some default data"
    # Not a permission error.
    raise
else:
    with fp:
        return fp.read()

Nota

I/O operations may fail even when access() indicates that they would succeed, particularly for operations on network filesystems which may have permissions semantics beyond the usual POSIX permission-bit model.

os.F_OK

Value to pass as the mode parameter of access() to test the existence of path.

os.R_OK

Value to include in the mode parameter of access() to test the readability of path.

os.W_OK

Value to include in the mode parameter of access() to test the writability of path.

os.X_OK

Value to include in the mode parameter of access() to determine if path can be executed.

os.chdir(path)

Change the current working directory to path.

Disponibilidade: Unix, Windows.

os.fchdir(fd)

Change the current working directory to the directory represented by the file descriptor fd. The descriptor must refer to an opened directory, not an open file.

Disponibilidade: Unix.

Novo na versão 2.3.

os.getcwd()

Return a string representing the current working directory.

Disponibilidade: Unix, Windows.

os.getcwdu()

Return a Unicode object representing the current working directory.

Disponibilidade: Unix, Windows.

Novo na versão 2.3.

os.chflags(path, flags)

Set the flags of path to the numeric flags. flags may take a combination (bitwise OR) of the following values (as defined in the stat module):

Disponibilidade: Unix.

Novo na versão 2.6.

os.chroot(path)

Change the root directory of the current process to path. Availability: Unix.

Novo na versão 2.2.

os.chmod(path, mode)

Change the mode of path to the numeric mode. mode may take one of the following values (as defined in the stat module) or bitwise ORed combinations of them:

Disponibilidade: Unix, Windows.

Nota

Although Windows supports chmod(), you can only set the file’s read-only flag with it (via the stat.S_IWRITE and stat.S_IREAD constants or a corresponding integer value). All other bits are ignored.

os.chown(path, uid, gid)

Change the owner and group id of path to the numeric uid and gid. To leave one of the ids unchanged, set it to -1.

Disponibilidade: Unix.

os.lchflags(path, flags)

Set the flags of path to the numeric flags, like chflags(), but do not follow symbolic links.

Disponibilidade: Unix.

Novo na versão 2.6.

os.lchmod(path, mode)

Change the mode of path to the numeric mode. If path is a symlink, this affects the symlink rather than the target. See the docs for chmod() for possible values of mode.

Disponibilidade: Unix.

Novo na versão 2.6.

os.lchown(path, uid, gid)

Change the owner and group id of path to the numeric uid and gid. This function will not follow symbolic links.

Disponibilidade: Unix.

Novo na versão 2.3.

Create a hard link pointing to source named link_name.

Disponibilidade: Unix.

os.listdir(path)

Return a list containing the names of the entries in the directory given by path. The list is in arbitrary order. It does not include the special entries '.' and '..' even if they are present in the directory.

Disponibilidade: Unix, Windows.

Alterado na versão 2.3: On Windows NT/2k/XP and Unix, if path is a Unicode object, the result will be a list of Unicode objects. Undecodable filenames will still be returned as string objects.

os.lstat(path)

Perform the equivalent of an lstat() system call on the given path. Similar to stat(), but does not follow symbolic links. On platforms that do not support symbolic links, this is an alias for stat().

os.mkfifo(path[, mode])

Create a FIFO (a named pipe) named path with numeric mode mode. The default mode is 0666 (octal). The current umask value is first masked out from the mode.

Disponibilidade: Unix.

FIFOs are pipes that can be accessed like regular files. FIFOs exist until they are deleted (for example with os.unlink()). Generally, FIFOs are used as rendezvous between “client” and “server” type processes: the server opens the FIFO for reading, and the client opens it for writing. Note that mkfifo() doesn’t open the FIFO — it just creates the rendezvous point.

os.mknod(filename[, mode=0600[, device=0]])

Create a filesystem node (file, device special file or named pipe) named filename. mode specifies both the permissions to use and the type of node to be created, being combined (bitwise OR) with one of stat.S_IFREG, stat.S_IFCHR, stat.S_IFBLK, and stat.S_IFIFO (those constants are available in stat). For stat.S_IFCHR and stat.S_IFBLK, device defines the newly created device special file (probably using os.makedev()), otherwise it is ignored.

Novo na versão 2.3.

os.major(device)

Extract the device major number from a raw device number (usually the st_dev or st_rdev field from stat).

Novo na versão 2.3.

os.minor(device)

Extract the device minor number from a raw device number (usually the st_dev or st_rdev field from stat).

Novo na versão 2.3.

os.makedev(major, minor)

Compose a raw device number from the major and minor device numbers.

Novo na versão 2.3.

os.mkdir(path[, mode])

Create a directory named path with numeric mode mode. The default mode is 0777 (octal). If the directory already exists, OSError is raised.

On some systems, mode is ignored. Where it is used, the current umask value is first masked out. If bits other than the last 9 (i.e. the last 3 digits of the octal representation of the mode) are set, their meaning is platform-dependent. On some platforms, they are ignored and you should call chmod() explicitly to set them.

It is also possible to create temporary directories; see the tempfile module’s tempfile.mkdtemp() function.

Disponibilidade: Unix, Windows.

os.makedirs(path[, mode])

Recursive directory creation function. Like mkdir(), but makes all intermediate-level directories needed to contain the leaf directory. Raises an error exception if the leaf directory already exists or cannot be created. The default mode is 0777 (octal).

The mode parameter is passed to mkdir(); see the mkdir() description for how it is interpreted.

Nota

makedirs() will become confused if the path elements to create include os.pardir.

Novo na versão 1.5.2.

Alterado na versão 2.3: This function now handles UNC paths correctly.

os.pathconf(path, name)

Return system configuration information relevant to a named file. name specifies the configuration value to retrieve; it may be a string which is the name of a defined system value; these names are specified in a number of standards (POSIX.1, Unix 95, Unix 98, and others). Some platforms define additional names as well. The names known to the host operating system are given in the pathconf_names dictionary. For configuration variables not included in that mapping, passing an integer for name is also accepted.

Se name for uma string e não for conhecida, ValueError é gerado. Se um valor específico para name não for compatível com o sistema de host, mesmo que seja incluído no pathconf_names, um erro OSError é gerado com errno.EINVAL como número do erro.

Disponibilidade: Unix.

os.pathconf_names

Dictionary mapping names accepted by pathconf() and fpathconf() to the integer values defined for those names by the host operating system. This can be used to determine the set of names known to the system. Availability: Unix.

Return a string representing the path to which the symbolic link points. The result may be either an absolute or relative pathname; if it is relative, it may be converted to an absolute pathname using os.path.join(os.path.dirname(path), result).

Alterado na versão 2.6: If the path is a Unicode object the result will also be a Unicode object.

Disponibilidade: Unix.

os.remove(path)

Remove (delete) the file path. If path is a directory, OSError is raised; see rmdir() below to remove a directory. This is identical to the unlink() function documented below. On Windows, attempting to remove a file that is in use causes an exception to be raised; on Unix, the directory entry is removed but the storage allocated to the file is not made available until the original file is no longer in use.

Disponibilidade: Unix, Windows.

os.removedirs(path)

Remove directories recursively. Works like rmdir() except that, if the leaf directory is successfully removed, removedirs() tries to successively remove every parent directory mentioned in path until an error is raised (which is ignored, because it generally means that a parent directory is not empty). For example, os.removedirs('foo/bar/baz') will first remove the directory 'foo/bar/baz', and then remove 'foo/bar' and 'foo' if they are empty. Raises OSError if the leaf directory could not be successfully removed.

Novo na versão 1.5.2.

os.rename(src, dst)

Rename the file or directory src to dst. If dst is a directory, OSError will be raised. On Unix, if dst exists and is a file, it will be replaced silently if the user has permission. The operation may fail on some Unix flavors if src and dst are on different filesystems. If successful, the renaming will be an atomic operation (this is a POSIX requirement). On Windows, if dst already exists, OSError will be raised even if it is a file; there may be no way to implement an atomic rename when dst names an existing file.

Disponibilidade: Unix, Windows.

os.renames(old, new)

Recursive directory or file renaming function. Works like rename(), except creation of any intermediate directories needed to make the new pathname good is attempted first. After the rename, directories corresponding to rightmost path segments of the old name will be pruned away using removedirs().

Novo na versão 1.5.2.

Nota

This function can fail with the new directory structure made if you lack permissions needed to remove the leaf directory or file.

os.rmdir(path)

Remove (delete) the directory path. Only works when the directory is empty, otherwise, OSError is raised. In order to remove whole directory trees, shutil.rmtree() can be used.

Disponibilidade: Unix, Windows.

os.stat(path)

Perform the equivalent of a stat() system call on the given path. (This function follows symlinks; to stat a symlink use lstat().)

The return value is an object whose attributes correspond to the members of the stat structure, namely:

  • st_mode - protection bits,

  • st_ino - inode number,

  • st_dev - device,

  • st_nlink - number of hard links,

  • st_uid - user id of owner,

  • st_gid - group id of owner,

  • st_size - size of file, in bytes,

  • st_atime - time of most recent access,

  • st_mtime - time of most recent content modification,

  • st_ctime - platform dependent; time of most recent metadata change on Unix, or the time of creation on Windows)

Alterado na versão 2.3: If stat_float_times() returns True, the time values are floats, measuring seconds. Fractions of a second may be reported if the system supports that. See stat_float_times() for further discussion.

On some Unix systems (such as Linux), the following attributes may also be available:

  • st_blocks - number of 512-byte blocks allocated for file

  • st_blksize - filesystem blocksize for efficient file system I/O

  • st_rdev - type of device if an inode device

  • st_flags - user defined flags for file

On other Unix systems (such as FreeBSD), the following attributes may be available (but may be only filled out if root tries to use them):

  • st_gen - file generation number

  • st_birthtime - time of file creation

On RISCOS systems, the following attributes are also available:

  • st_ftype (file type)

  • st_attrs (attributes)

  • st_obtype (object type).

Nota

The exact meaning and resolution of the st_atime, st_mtime, and st_ctime attributes depend on the operating system and the file system. For example, on Windows systems using the FAT or FAT32 file systems, st_mtime has 2-second resolution, and st_atime has only 1-day resolution. See your operating system documentation for details.

For backward compatibility, the return value of stat() is also accessible as a tuple of at least 10 integers giving the most important (and portable) members of the stat structure, in the order st_mode, st_ino, st_dev, st_nlink, st_uid, st_gid, st_size, st_atime, st_mtime, st_ctime. More items may be added at the end by some implementations.

The standard module stat defines functions and constants that are useful for extracting information from a stat structure. (On Windows, some items are filled with dummy values.)

Exemplo:

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
(33188, 422511, 769, 1, 1032, 100, 926, 1105022698,1105022732, 1105022732)
>>> statinfo.st_size
926

Disponibilidade: Unix, Windows.

Alterado na versão 2.2: Added access to values as attributes of the returned object.

Alterado na versão 2.5: Added st_gen and st_birthtime.

os.stat_float_times([newvalue])

Determine whether stat_result represents time stamps as float objects. If newvalue is True, future calls to stat() return floats, if it is False, future calls return ints. If newvalue is omitted, return the current setting.

For compatibility with older Python versions, accessing stat_result as a tuple always returns integers.

Alterado na versão 2.5: Python now returns float values by default. Applications which do not work correctly with floating point time stamps can use this function to restore the old behaviour.

The resolution of the timestamps (that is the smallest possible fraction) depends on the system. Some systems only support second resolution; on these systems, the fraction will always be zero.

It is recommended that this setting is only changed at program startup time in the __main__ module; libraries should never change this setting. If an application uses a library that works incorrectly if floating point time stamps are processed, this application should turn the feature off until the library has been corrected.

os.statvfs(path)

Perform a statvfs() system call on the given path. The return value is an object whose attributes describe the filesystem on the given path, and correspond to the members of the statvfs structure, namely: f_bsize, f_frsize, f_blocks, f_bfree, f_bavail, f_files, f_ffree, f_favail, f_flag, f_namemax.

For backward compatibility, the return value is also accessible as a tuple whose values correspond to the attributes, in the order given above. The standard module statvfs defines constants that are useful for extracting information from a statvfs structure when accessing it as a sequence; this remains useful when writing code that needs to work with versions of Python that don’t support accessing the fields as attributes.

Disponibilidade: Unix.

Alterado na versão 2.2: Added access to values as attributes of the returned object.

Create a symbolic link pointing to source named link_name.

Disponibilidade: Unix.

os.tempnam([dir[, prefix]])

Return a unique path name that is reasonable for creating a temporary file. This will be an absolute path that names a potential directory entry in the directory dir or a common location for temporary files if dir is omitted or None. If given and not None, prefix is used to provide a short prefix to the filename. Applications are responsible for properly creating and managing files created using paths returned by tempnam(); no automatic cleanup is provided. On Unix, the environment variable TMPDIR overrides dir, while on Windows TMP is used. The specific behavior of this function depends on the C library implementation; some aspects are underspecified in system documentation.

Aviso

Use of tempnam() is vulnerable to symlink attacks; consider using tmpfile() (section Criação de Objetos Files) instead.

Disponibilidade: Unix, Windows.

os.tmpnam()

Return a unique path name that is reasonable for creating a temporary file. This will be an absolute path that names a potential directory entry in a common location for temporary files. Applications are responsible for properly creating and managing files created using paths returned by tmpnam(); no automatic cleanup is provided.

Aviso

Use of tmpnam() is vulnerable to symlink attacks; consider using tmpfile() (section Criação de Objetos Files) instead.

Availability: Unix, Windows. This function probably shouldn’t be used on Windows, though: Microsoft’s implementation of tmpnam() always creates a name in the root directory of the current drive, and that’s generally a poor location for a temp file (depending on privileges, you may not even be able to open a file using this name).

os.TMP_MAX

The maximum number of unique names that tmpnam() will generate before reusing names.

Remove (delete) the file path. This is the same function as remove(); the unlink() name is its traditional Unix name.

Disponibilidade: Unix, Windows.

os.utime(path, times)

Set the access and modified times of the file specified by path. If times is None, then the file’s access and modified times are set to the current time. (The effect is similar to running the Unix program touch on the path.) Otherwise, times must be a 2-tuple of numbers, of the form (atime, mtime) which is used to set the access and modified times, respectively. Whether a directory can be given for path depends on whether the operating system implements directories as files (for example, Windows does not). Note that the exact times you set here may not be returned by a subsequent stat() call, depending on the resolution with which your operating system records access and modification times; see stat().

Alterado na versão 2.0: Added support for None for times.

Disponibilidade: Unix, Windows.

os.walk(top, topdown=True, onerror=None, followlinks=False)

Generate the file names in a directory tree by walking the tree either top-down or bottom-up. For each directory in the tree rooted at directory top (including top itself), it yields a 3-tuple (dirpath, dirnames, filenames).

dirpath is a string, the path to the directory. dirnames is a list of the names of the subdirectories in dirpath (excluding '.' and '..'). filenames is a list of the names of the non-directory files in dirpath. Note that the names in the lists contain no path components. To get a full path (which begins with top) to a file or directory in dirpath, do os.path.join(dirpath, name).

If optional argument topdown is True or not specified, the triple for a directory is generated before the triples for any of its subdirectories (directories are generated top-down). If topdown is False, the triple for a directory is generated after the triples for all of its subdirectories (directories are generated bottom-up). No matter the value of topdown, the list of subdirectories is retrieved before the tuples for the directory and its subdirectories are generated.

When topdown is True, the caller can modify the dirnames list in-place (perhaps using del or slice assignment), and walk() will only recurse into the subdirectories whose names remain in dirnames; this can be used to prune the search, impose a specific order of visiting, or even to inform walk() about directories the caller creates or renames before it resumes walk() again. Modifying dirnames when topdown is False has no effect on the behavior of the walk, because in bottom-up mode the directories in dirnames are generated before dirpath itself is generated.

By default, errors from the listdir() call are ignored. If optional argument onerror is specified, it should be a function; it will be called with one argument, an OSError instance. It can report the error to continue with the walk, or raise the exception to abort the walk. Note that the filename is available as the filename attribute of the exception object.

By default, walk() will not walk down into symbolic links that resolve to directories. Set followlinks to True to visit directories pointed to by symlinks, on systems that support them.

Novo na versão 2.6: The followlinks parameter.

Nota

Be aware that setting followlinks to True can lead to infinite recursion if a link points to a parent directory of itself. walk() does not keep track of the directories it visited already.

Nota

If you pass a relative pathname, don’t change the current working directory between resumptions of walk(). walk() never changes the current directory, and assumes that its caller doesn’t either.

This example displays the number of bytes taken by non-directory files in each directory under the starting directory, except that it doesn’t look under any CVS subdirectory:

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print root, "consumes",
    print sum(getsize(join(root, name)) for name in files),
    print "bytes in", len(files), "non-directory files"
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

In the next example, walking the tree bottom-up is essential: rmdir() doesn’t allow deleting a directory before the directory is empty:

# Delete everything reachable from the directory named in "top",
# assuming there are no symbolic links.
# CAUTION:  This is dangerous!  For example, if top == '/', it
# could delete all your disk files.
import os
for root, dirs, files in os.walk(top, topdown=False):
    for name in files:
        os.remove(os.path.join(root, name))
    for name in dirs:
        os.rmdir(os.path.join(root, name))

Novo na versão 2.3.

15.1.5. Process Management

These functions may be used to create and manage processes.

The various exec* functions take a list of arguments for the new program loaded into the process. In each case, the first of these arguments is passed to the new program as its own name rather than as an argument a user may have typed on a command line. For the C programmer, this is the argv[0] passed to a program’s main(). For example, os.execv('/bin/echo', ['foo', 'bar']) will only print bar on standard output; foo will seem to be ignored.

os.abort()

Generate a SIGABRT signal to the current process. On Unix, the default behavior is to produce a core dump; on Windows, the process immediately returns an exit code of 3. Be aware that calling this function will not call the Python signal handler registered for SIGABRT with signal.signal().

Disponibilidade: Unix, Windows.

os.execl(path, arg0, arg1, ...)
os.execle(path, arg0, arg1, ..., env)
os.execlp(file, arg0, arg1, ...)
os.execlpe(file, arg0, arg1, ..., env)
os.execv(path, args)
os.execve(path, args, env)
os.execvp(file, args)
os.execvpe(file, args, env)

These functions all execute a new program, replacing the current process; they do not return. On Unix, the new executable is loaded into the current process, and will have the same process id as the caller. Errors will be reported as OSError exceptions.

The current process is replaced immediately. Open file objects and descriptors are not flushed, so if there may be data buffered on these open files, you should flush them using sys.stdout.flush() or os.fsync() before calling an exec* function.

The “l” and “v” variants of the exec* functions differ in how command-line arguments are passed. The “l” variants are perhaps the easiest to work with if the number of parameters is fixed when the code is written; the individual parameters simply become additional parameters to the execl*() functions. The “v” variants are good when the number of parameters is variable, with the arguments being passed in a list or tuple as the args parameter. In either case, the arguments to the child process should start with the name of the command being run, but this is not enforced.

The variants which include a “p” near the end (execlp(), execlpe(), execvp(), and execvpe()) will use the PATH environment variable to locate the program file. When the environment is being replaced (using one of the exec*e variants, discussed in the next paragraph), the new environment is used as the source of the PATH variable. The other variants, execl(), execle(), execv(), and execve(), will not use the PATH variable to locate the executable; path must contain an appropriate absolute or relative path.

For execle(), execlpe(), execve(), and execvpe() (note that these all end in “e”), the env parameter must be a mapping which is used to define the environment variables for the new process (these are used instead of the current process’ environment); the functions execl(), execlp(), execv(), and execvp() all cause the new process to inherit the environment of the current process.

Disponibilidade: Unix, Windows.

os._exit(n)

Exit the process with status n, without calling cleanup handlers, flushing stdio buffers, etc.

Disponibilidade: Unix, Windows.

Nota

The standard way to exit is sys.exit(n). _exit() should normally only be used in the child process after a fork().

The following exit codes are defined and can be used with _exit(), although they are not required. These are typically used for system programs written in Python, such as a mail server’s external command delivery program.

Nota

Some of these may not be available on all Unix platforms, since there is some variation. These constants are defined where they are defined by the underlying platform.

os.EX_OK

Exit code that means no error occurred.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_USAGE

Exit code that means the command was used incorrectly, such as when the wrong number of arguments are given.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_DATAERR

Exit code that means the input data was incorrect.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_NOINPUT

Exit code that means an input file did not exist or was not readable.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_NOUSER

Exit code that means a specified user did not exist.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_NOHOST

Exit code that means a specified host did not exist.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_UNAVAILABLE

Exit code that means that a required service is unavailable.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_SOFTWARE

Exit code that means an internal software error was detected.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_OSERR

Exit code that means an operating system error was detected, such as the inability to fork or create a pipe.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_OSFILE

Exit code that means some system file did not exist, could not be opened, or had some other kind of error.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_CANTCREAT

Exit code that means a user specified output file could not be created.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_IOERR

Exit code that means that an error occurred while doing I/O on some file.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_TEMPFAIL

Exit code that means a temporary failure occurred. This indicates something that may not really be an error, such as a network connection that couldn’t be made during a retryable operation.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_PROTOCOL

Exit code that means that a protocol exchange was illegal, invalid, or not understood.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_NOPERM

Exit code that means that there were insufficient permissions to perform the operation (but not intended for file system problems).

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_CONFIG

Exit code that means that some kind of configuration error occurred.

Disponibilidade: Unix.

Novo na versão 2.3.

os.EX_NOTFOUND

Exit code that means something like “an entry was not found”.

Disponibilidade: Unix.

Novo na versão 2.3.

os.fork()

Fork a child process. Return 0 in the child and the child’s process id in the parent. If an error occurs OSError is raised.

Note that some platforms including FreeBSD <= 6.3, Cygwin and OS/2 EMX have known issues when using fork() from a thread.

Aviso

See ssl for applications that use the SSL module with fork().

Disponibilidade: Unix.

os.forkpty()

Fork a child process, using a new pseudo-terminal as the child’s controlling terminal. Return a pair of (pid, fd), where pid is 0 in the child, the new child’s process id in the parent, and fd is the file descriptor of the master end of the pseudo-terminal. For a more portable approach, use the pty module. If an error occurs OSError is raised.

Disponibilidade: alguns sabores de Unix

os.kill(pid, sig)

Send signal sig to the process pid. Constants for the specific signals available on the host platform are defined in the signal module.

Windows: The signal.CTRL_C_EVENT and signal.CTRL_BREAK_EVENT signals are special signals which can only be sent to console processes which share a common console window, e.g., some subprocesses. Any other value for sig will cause the process to be unconditionally killed by the TerminateProcess API, and the exit code will be set to sig. The Windows version of kill() additionally takes process handles to be killed.

Novo na versão 2.7: Windows support

os.killpg(pgid, sig)

Envia o sinal sig para o grupo de processo pgid.

Disponibilidade: Unix.

Novo na versão 2.3.

os.nice(increment)

Add increment to the process’s “niceness”. Return the new niceness.

Disponibilidade: Unix.

os.plock(op)

Lock program segments into memory. The value of op (defined in <sys/lock.h>) determines which segments are locked.

Disponibilidade: Unix.

os.popen(...)
os.popen2(...)
os.popen3(...)
os.popen4(...)

Run child processes, returning opened pipes for communications. These functions are described in section Criação de Objetos Files.

os.spawnl(mode, path, ...)
os.spawnle(mode, path, ..., env)
os.spawnlp(mode, file, ...)
os.spawnlpe(mode, file, ..., env)
os.spawnv(mode, path, args)
os.spawnve(mode, path, args, env)
os.spawnvp(mode, file, args)
os.spawnvpe(mode, file, args, env)

Execute the program path in a new process.

(Note that the subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using these functions. Check especially the Replacing Older Functions with the subprocess Module section.)

If mode is P_NOWAIT, this function returns the process id of the new process; if mode is P_WAIT, returns the process’s exit code if it exits normally, or -signal, where signal is the signal that killed the process. On Windows, the process id will actually be the process handle, so can be used with the waitpid() function.

The “l” and “v” variants of the spawn* functions differ in how command-line arguments are passed. The “l” variants are perhaps the easiest to work with if the number of parameters is fixed when the code is written; the individual parameters simply become additional parameters to the spawnl*() functions. The “v” variants are good when the number of parameters is variable, with the arguments being passed in a list or tuple as the args parameter. In either case, the arguments to the child process must start with the name of the command being run.

The variants which include a second “p” near the end (spawnlp(), spawnlpe(), spawnvp(), and spawnvpe()) will use the PATH environment variable to locate the program file. When the environment is being replaced (using one of the spawn*e variants, discussed in the next paragraph), the new environment is used as the source of the PATH variable. The other variants, spawnl(), spawnle(), spawnv(), and spawnve(), will not use the PATH variable to locate the executable; path must contain an appropriate absolute or relative path.

For spawnle(), spawnlpe(), spawnve(), and spawnvpe() (note that these all end in “e”), the env parameter must be a mapping which is used to define the environment variables for the new process (they are used instead of the current process’ environment); the functions spawnl(), spawnlp(), spawnv(), and spawnvp() all cause the new process to inherit the environment of the current process. Note that keys and values in the env dictionary must be strings; invalid keys or values will cause the function to fail, with a return value of 127.

As an example, the following calls to spawnlp() and spawnvpe() are equivalent:

import os
os.spawnlp(os.P_WAIT, 'cp', 'cp', 'index.html', '/dev/null')

L = ['cp', 'index.html', '/dev/null']
os.spawnvpe(os.P_WAIT, 'cp', L, os.environ)

Availability: Unix, Windows. spawnlp(), spawnlpe(), spawnvp() and spawnvpe() are not available on Windows. spawnle() and spawnve() are not thread-safe on Windows; we advise you to use the subprocess module instead.

Novo na versão 1.6.

os.P_NOWAIT
os.P_NOWAITO

Possible values for the mode parameter to the spawn* family of functions. If either of these values is given, the spawn*() functions will return as soon as the new process has been created, with the process id as the return value.

Disponibilidade: Unix, Windows.

Novo na versão 1.6.

os.P_WAIT

Possible value for the mode parameter to the spawn* family of functions. If this is given as mode, the spawn*() functions will not return until the new process has run to completion and will return the exit code of the process the run is successful, or -signal if a signal kills the process.

Disponibilidade: Unix, Windows.

Novo na versão 1.6.

os.P_DETACH
os.P_OVERLAY

Possible values for the mode parameter to the spawn* family of functions. These are less portable than those listed above. P_DETACH is similar to P_NOWAIT, but the new process is detached from the console of the calling process. If P_OVERLAY is used, the current process will be replaced; the spawn*() function will not return.

Availability: Windows.

Novo na versão 1.6.

os.startfile(path[, operation])

Start a file with its associated application.

When operation is not specified or 'open', this acts like double-clicking the file in Windows Explorer, or giving the file name as an argument to the start command from the interactive command shell: the file is opened with whatever application (if any) its extension is associated.

When another operation is given, it must be a “command verb” that specifies what should be done with the file. Common verbs documented by Microsoft are 'print' and 'edit' (to be used on files) as well as 'explore' and 'find' (to be used on directories).

startfile() returns as soon as the associated application is launched. There is no option to wait for the application to close, and no way to retrieve the application’s exit status. The path parameter is relative to the current directory. If you want to use an absolute path, make sure the first character is not a slash ('/'); the underlying Win32 ShellExecute() function doesn’t work if it is. Use the os.path.normpath() function to ensure that the path is properly encoded for Win32.

Availability: Windows.

Novo na versão 2.0.

Novo na versão 2.5: The operation parameter.

os.system(command)

Execute the command (a string) in a subshell. This is implemented by calling the Standard C function system(), and has the same limitations. Changes to sys.stdin, etc. are not reflected in the environment of the executed command.

On Unix, the return value is the exit status of the process encoded in the format specified for wait(). Note that POSIX does not specify the meaning of the return value of the C system() function, so the return value of the Python function is system-dependent.

On Windows, the return value is that returned by the system shell after running command, given by the Windows environment variable COMSPEC: on command.com systems (Windows 95, 98 and ME) this is always 0; on cmd.exe systems (Windows NT, 2000 and XP) this is the exit status of the command run; on systems using a non-native shell, consult your shell documentation.

The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function. See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes.

Disponibilidade: Unix, Windows.

os.times()

Return a 5-tuple of floating point numbers indicating accumulated (processor or other) times, in seconds. The items are: user time, system time, children’s user time, children’s system time, and elapsed real time since a fixed point in the past, in that order. See the Unix manual page times(2) or the corresponding Windows Platform API documentation. On Windows, only the first two items are filled, the others are zero.

Disponibilidade: Unix, Windows

os.wait()

Wait for completion of a child process, and return a tuple containing its pid and exit status indication: a 16-bit number, whose low byte is the signal number that killed the process, and whose high byte is the exit status (if the signal number is zero); the high bit of the low byte is set if a core file was produced.

Disponibilidade: Unix.

os.waitpid(pid, options)

The details of this function differ on Unix and Windows.

On Unix: Wait for completion of a child process given by process id pid, and return a tuple containing its process id and exit status indication (encoded as for wait()). The semantics of the call are affected by the value of the integer options, which should be 0 for normal operation.

If pid is greater than 0, waitpid() requests status information for that specific process. If pid is 0, the request is for the status of any child in the process group of the current process. If pid is -1, the request pertains to any child of the current process. If pid is less than -1, status is requested for any process in the process group -pid (the absolute value of pid).

An OSError is raised with the value of errno when the syscall returns -1.

On Windows: Wait for completion of a process given by process handle pid, and return a tuple containing pid, and its exit status shifted left by 8 bits (shifting makes cross-platform use of the function easier). A pid less than or equal to 0 has no special meaning on Windows, and raises an exception. The value of integer options has no effect. pid can refer to any process whose id is known, not necessarily a child process. The spawn* functions called with P_NOWAIT return suitable process handles.

os.wait3(options)

Similar to waitpid(), except no process id argument is given and a 3-element tuple containing the child’s process id, exit status indication, and resource usage information is returned. Refer to resource.getrusage() for details on resource usage information. The option argument is the same as that provided to waitpid() and wait4().

Disponibilidade: Unix.

Novo na versão 2.5.

os.wait4(pid, options)

Similar to waitpid(), except a 3-element tuple, containing the child’s process id, exit status indication, and resource usage information is returned. Refer to resource.getrusage() for details on resource usage information. The arguments to wait4() are the same as those provided to waitpid().

Disponibilidade: Unix.

Novo na versão 2.5.

os.WNOHANG

The option for waitpid() to return immediately if no child process status is available immediately. The function returns (0, 0) in this case.

Disponibilidade: Unix.

os.WCONTINUED

This option causes child processes to be reported if they have been continued from a job control stop since their status was last reported.

Availability: Some Unix systems.

Novo na versão 2.3.

os.WUNTRACED

This option causes child processes to be reported if they have been stopped but their current state has not been reported since they were stopped.

Disponibilidade: Unix.

Novo na versão 2.3.

The following functions take a process status code as returned by system(), wait(), or waitpid() as a parameter. They may be used to determine the disposition of a process.

os.WCOREDUMP(status)

Return True if a core dump was generated for the process, otherwise return False.

Disponibilidade: Unix.

Novo na versão 2.3.

os.WIFCONTINUED(status)

Return True if the process has been continued from a job control stop, otherwise return False.

Disponibilidade: Unix.

Novo na versão 2.3.

os.WIFSTOPPED(status)

Return True if the process has been stopped, otherwise return False.

Disponibilidade: Unix.

os.WIFSIGNALED(status)

Return True if the process exited due to a signal, otherwise return False.

Disponibilidade: Unix.

os.WIFEXITED(status)

Return True if the process exited using the exit(2) system call, otherwise return False.

Disponibilidade: Unix.

os.WEXITSTATUS(status)

If WIFEXITED(status) is true, return the integer parameter to the exit(2) system call. Otherwise, the return value is meaningless.

Disponibilidade: Unix.

os.WSTOPSIG(status)

Return the signal which caused the process to stop.

Disponibilidade: Unix.

os.WTERMSIG(status)

Return the signal which caused the process to exit.

Disponibilidade: Unix.

15.1.6. Informações Diversas do Sistema

os.confstr(name)

Return string-valued system configuration values. name specifies the configuration value to retrieve; it may be a string which is the name of a defined system value; these names are specified in a number of standards (POSIX, Unix 95, Unix 98, and others). Some platforms define additional names as well. The names known to the host operating system are given as the keys of the confstr_names dictionary. For configuration variables not included in that mapping, passing an integer for name is also accepted.

Se o valor de configuração especificado por name não for definido, retorna None.

If name is a string and is not known, ValueError is raised. If a specific value for name is not supported by the host system, even if it is included in confstr_names, an OSError is raised with errno.EINVAL for the error number.

Disponibilidade: Unix

os.confstr_names

Dictionary mapping names accepted by confstr() to the integer values defined for those names by the host operating system. This can be used to determine the set of names known to the system.

Disponibilidade: Unix.

os.getloadavg()

Return the number of processes in the system run queue averaged over the last 1, 5, and 15 minutes or raises OSError if the load average was unobtainable.

Disponibilidade: Unix.

Novo na versão 2.3.

os.sysconf(name)

Return integer-valued system configuration values. If the configuration value specified by name isn’t defined, -1 is returned. The comments regarding the name parameter for confstr() apply here as well; the dictionary that provides information on the known names is given by sysconf_names.

Disponibilidade: Unix.

os.sysconf_names

Dictionary mapping names accepted by sysconf() to the integer values defined for those names by the host operating system. This can be used to determine the set of names known to the system.

Disponibilidade: Unix.

Os dados a seguir são usados para suportar operações de manipulação de path. Estão definidos e disponíveis para todas as plataformas.

Higher-level operations on pathnames are defined in the os.path module.

os.curdir

The constant string used by the operating system to refer to the current directory. This is '.' for Windows and POSIX. Also available via os.path.

os.pardir

The constant string used by the operating system to refer to the parent directory. This is '..' for Windows and POSIX. Also available via os.path.

os.sep

The character used by the operating system to separate pathname components. This is '/' for POSIX and '\\' for Windows. Note that knowing this is not sufficient to be able to parse or concatenate pathnames — use os.path.split() and os.path.join() — but it is occasionally useful. Also available via os.path.

os.altsep

An alternative character used by the operating system to separate pathname components, or None if only one separator character exists. This is set to '/' on Windows systems where sep is a backslash. Also available via os.path.

os.extsep

The character which separates the base filename from the extension; for example, the '.' in os.py. Also available via os.path.

Novo na versão 2.2.

os.pathsep

The character conventionally used by the operating system to separate search path components (as in PATH), such as ':' for POSIX or ';' for Windows. Also available via os.path.

os.defpath

The default search path used by exec*p* and spawn*p* if the environment doesn’t have a 'PATH' key. Also available via os.path.

os.linesep

The string used to separate (or, rather, terminate) lines on the current platform. This may be a single character, such as '\n' for POSIX, or multiple characters, for example, '\r\n' for Windows. Do not use os.linesep as a line terminator when writing files opened in text mode (the default); use a single '\n' instead, on all platforms.

os.devnull

The file path of the null device. For example: '/dev/null' for POSIX, 'nul' for Windows. Also available via os.path.

Novo na versão 2.4.

15.1.7. Miscellaneous Functions

os.urandom(n)

Return a string of n random bytes suitable for cryptographic use.

This function returns random bytes from an OS-specific randomness source. The returned data should be unpredictable enough for cryptographic applications, though its exact quality depends on the OS implementation. On a UNIX-like system this will query /dev/urandom, and on Windows it will use CryptGenRandom(). If a randomness source is not found, NotImplementedError will be raised.

For an easy-to-use interface to the random number generator provided by your platform, please see random.SystemRandom.

Novo na versão 2.4.