Built-in Module posix

posix

This module provides access to operating system functionality that is standardized by the C Standard and the POSIX standard (a thinly diguised interface). It is available in all Python versions except on the Macintosh; the MS-DOS version does not support certain functions. The descriptions below are very terse; refer to the corresponding manual entry for more information.

Errors are reported as exceptions; the usual exceptions are given for type errors, while errors reported by the system calls raise posix.error, described below.

Module posix defines the following data items:


\begin{datadesc}{environ} A dictionary representing the string environment at th... ... your home directory, equivalent to \code{getenv(''HOME'')} in C. \end{datadesc}


\begin{excdesc}{error} This exception is raised when an POSIX function returns a... ...ing string, as would be printed by the C function \code{perror()}. \end{excdesc}

It defines the following functions:


\begin{funcdesc}{chdir}{path} Change the current working directory to \var{path}. \end{funcdesc}


\begin{funcdesc}{chmod}{path\, mode} Change the mode of \var{path} to the numeric \var{mode}. \end{funcdesc}


\begin{funcdesc}{close}{fd} Close file descriptor \var{fd}. \end{funcdesc}


\begin{funcdesc}{dup}{fd} Return a duplicate of file descriptor \var{fd}. \end{funcdesc}


\begin{funcdesc}{dup2}{fd\, fd2} Duplicate file descriptor \var{fd} to \var{fd2}, closing the latter first if necessary. Return \code{None}. \end{funcdesc}


\begin{funcdesc}{execv}{path\, args} Execute the executable \var{path} with argu... ...argument list may be a tuple or list of strings. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{execve}{path\, args\, env} Execute the executable \var{path} wi... ...must be a dictionary mapping strings to strings. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{_exit}{n} Exit to the system with status \var{n}, without calli... ...normally only be used in the child process after a \code{fork()}. \end{funcdesc}


\begin{funcdesc}{fdopen}{fd\, mode} Return an open file object connected to the ... ...s the \var{mode} argument to the built-in \code{open()} function. \end{funcdesc}


\begin{funcdesc}{fork}{} Fork a child process. Return 0 in the child, the child's process id in the parent. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{fstat}{fd} Return status for file descriptor \var{fd}, like \code{stat()}. \end{funcdesc}


\begin{funcdesc}{getcwd}{} Return a string representing the current working directory. \end{funcdesc}


\begin{funcdesc}{getegid}{} Return the current process's effective group id. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{geteuid}{} Return the current process's effective user id. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{getgid}{} Return the current process's group id. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{getpid}{} Return the current process id. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{getppid}{} Return the parent's process id. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{getuid}{} Return the current process's user id. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{kill}{pid\, sig} Kill the process \var{pid} with signal \var{sig}. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{link}{src\, dst} Create a hard link pointing to \var{src} named \var{dst}. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{listdir}{path} Return a list containing the names of the entrie... ... \code{'.'} and \code{'..'} if they are present in the directory. \end{funcdesc}


\begin{funcdesc}{lseek}{fd\, pos\, how} Set the current position of file descrip... ...he current position; 2 to set it relative to the end of the file. \end{funcdesc}


\begin{funcdesc}{lstat}{path} Like \code{stat()}, but do not follow symbolic lin... ... without symbolic links, this is identical to \code{posix.stat}.) \end{funcdesc}


\begin{funcdesc}{mkdir}{path\, mode} Create a directory named \var{path} with numeric mode \var{mode}. \end{funcdesc}


\begin{funcdesc}{nice}{increment} Add \var{incr} to the process' \lq\lq niceness''. Return the new niceness. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{open}{file\, flags\, mode} Open the file \var{file} and set var... ...\var{mode}. Return the file descriptor for the newly opened file. \end{funcdesc}


\begin{funcdesc}{pipe}{} Create a pipe. Return a pair of file descriptors \code{... ...)} usable for reading and writing, respectively. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{popen}{command\, mode} Open a pipe to or from \var{command}. Th... ... whether \var{mode} is \code{'r'} or \code{'w'}. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{read}{fd\, n} Read at most \var{n} bytes from file descriptor \var{fd}. Return a string containing the bytes read. \end{funcdesc}


\begin{funcdesc}{readlink}{path} Return a string representing the path to which ... ...s without symbolic links, this always raises \code{posix.error}.) \end{funcdesc}


\begin{funcdesc}{rename}{src\, dst} Rename the file or directory \var{src} to \var{dst}. \end{funcdesc}


\begin{funcdesc}{rmdir}{path} Remove the directory \var{path}. \end{funcdesc}


\begin{funcdesc}{setgid}{gid} Set the current process's group id. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{setuid}{uid} Set the current process's user id. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{stat}{path} Perform a {\em stat} system call on the given path.... ...that are useful for extracting information from a stat structure. \end{funcdesc}


\begin{funcdesc}{symlink}{src\, dst} Create a symbolic link pointing to \var{src... ...s without symbolic links, this always raises \code{posix.error}.) \end{funcdesc}


\begin{funcdesc}{system}{command} Execute the command (a string) in a subshell. ... ... status of the process as returned by Standard C \code{system()}. \end{funcdesc}


\begin{funcdesc}{times}{} Return a 4-tuple of floating point numbers indicating ... ...der. See the \UNIX{} manual page {\it times}(2). (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{umask}{mask} Set the current numeric umask and returns the previous umask. (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{uname}{} Return a 5-tuple containing information identifying th... ...et.gethostname()}. (Not on MS-DOS, nor on older \UNIX{} systems.) \end{funcdesc}


\begin{funcdesc}{unlink}{path} Unlink \var{path}. \end{funcdesc}


\begin{funcdesc}{utime}{path\, \(atime\, mtime\)} Set the access and modified ti... ... the given values. (The second argument is a tuple of two items.) \end{funcdesc}


\begin{funcdesc}{wait}{} Wait for completion of a child process, and return a tu... ... exit status indication (encoded as by \UNIX{}). (Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{waitpid}{pid\, options} Wait for completion of a child process ... ...waitpid(), this always raises \code{posix.error}. Not on MS-DOS.) \end{funcdesc}


\begin{funcdesc}{write}{fd\, str} Write the string \var{str} to file descriptor \var{fd}. Return the number of bytes actually written. \end{funcdesc}