Doc/lib/libos.tex

   1 \section{Standard Module \sectcode{os}}
   2
   3 \stmodindex{os}
   4 This module provides a more portable way of using operating system
   5 (OS) dependent functionality than importing an OS dependent built-in
   6 module like \code{posix}.
   7
   8 When the optional built-in module \code{posix} is available, this
   9 module exports the same functions and data as \code{posix}; otherwise,
  10 it searches for an OS dependent built-in module like \code{mac} and
  11 exports the same functions and data as found there.  The design of all
  12 Python's built-in OS dependent modules is such that as long as the same
  13 functionality is available, it uses the same interface; e.g., the
  14 function \code{os.stat(\var{file})} returns stat info about a \var{file} in a
  15 format compatible with the POSIX interface.
  16
  17 Extensions peculiar to a particular OS are also available through the
  18 \code{os} module, but using them is of course a threat to portability!
  19
  20 Note that after the first time \code{os} is imported, there is \emph{no}
  21 performance penalty in using functions from \code{os} instead of
  22 directly from the OS dependent built-in module, so there should be
  23 \emph{no} reason not to use \code{os}!
  24
  25 In addition to whatever the correct OS dependent module exports, the
  26 following variables and functions are always exported by \code{os}:
  27
  28 \renewcommand{\indexsubitem}{(in module os)}
  29
  30 \begin{datadesc}{name}
  31 The name of the OS dependent module imported.  The following names
  32 have currently been registered: \code{'posix'}, \code{'nt'},
  33 \code{'dos'}, \code{'mac'}.
  34 \end{datadesc}
  35
  36 \begin{datadesc}{path}
  37 The corresponding OS dependent standard module for pathname
  38 operations, e.g., \code{posixpath} or \code{macpath}.  Thus, (given
  39 the proper imports), \code{os.path.split(\var{file})} is equivalent to but
  40 more portable than \code{posixpath.split(\var{file})}.
  41 \end{datadesc}
  42
  43 \begin{datadesc}{curdir}
  44 The constant string used by the OS to refer to the current directory,
  45 e.g. \code{'.'} for POSIX or \code{':'} for the Mac.
  46 \end{datadesc}
  47
  48 \begin{datadesc}{pardir}
  49 The constant string used by the OS to refer to the parent directory,
  50 e.g. \code{'..'} for POSIX or \code{'::'} for the Mac.
  51 \end{datadesc}
  52
  53 \begin{datadesc}{sep}
  54 The character used by the OS to separate pathname components, e.g.\
  55 \code{'/'} for POSIX or \code{':'} for the Mac.  Note that knowing this
  56 is not sufficient to be able to parse or concatenate pathnames---better
  57 use \code{os.path.split()} and \code{os.path.join()}---but it is
  58 occasionally useful.
  59 \end{datadesc}
  60
  61 \begin{datadesc}{pathsep}
  62 The character conventionally used by the OS to separate search patch
  63 components (as in \code{\$PATH}), e.g.\ \code{':'} for POSIX or
  64 \code{';'} for MS-DOS.
  65 \end{datadesc}
  66
  67 \begin{datadesc}{defpath}
  68 The default search path used by \code{os.exec*p*()} if the environment
  69 doesn't have a \code{'PATH'} key.
  70 \end{datadesc}
  71
  72 \begin{funcdesc}{execl}{path\, arg0\, arg1\, ...}
  73 This is equivalent to
  74 \code{os.execv(\var{path}, (\var{arg0}, \var{arg1}, ...))}.
  75 \end{funcdesc}
  76
  77 \begin{funcdesc}{execle}{path\, arg0\, arg1\, ...\, env}
  78 This is equivalent to
  79 \code{os.execve(\var{path}, (\var{arg0}, \var{arg1}, ...), \var{env})}.
  80 \end{funcdesc}
  81
  82 \begin{funcdesc}{execlp}{path\, arg0\, arg1\, ...}
  83 This is equivalent to
  84 \code{os.execvp(\var{path}, (\var{arg0}, \var{arg1}, ...))}.
  85 \end{funcdesc}
  86
  87 \begin{funcdesc}{execvp}{path\, args}
  88 This is like \code{os.execv(\var{path}, \var{args})} but duplicates
  89 the shell's actions in searching for an executable file in a list of
  90 directories.  The directory list is obtained from
  91 \code{os.environ['PATH']}.
  92 \end{funcdesc}
  93
  94 \begin{funcdesc}{execvpe}{path\, args\, env}
  95 This is a cross between \code{os.execve()} and \code{os.execvp()}.
  96 The directory list is obtained from \code{\var{env}['PATH']}.
  97 \end{funcdesc}
  98
  99 (The functions \code{os.execv()} and \code{execve()} are not
 100 documented here, since they are implemented by the OS dependent
 101 module.  If the OS dependent module doesn't define either of these,
 102 the functions that rely on it will raise an exception.  They are
 103 documented in the section on module \code{posix}, together with all
 104 other functions that \code{os} imports from the OS dependent module.)