/[emacs]/emacs/lispref/files.texi
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revision 1.51 by rms, Tue Jun 24 18:16:37 2003 UTC revision 1.52 by rms, Mon Jul 7 20:48:26 2003 UTC
# Line 1809  default-directory Line 1809  default-directory
1809    
1810  @defun substitute-in-file-name filename  @defun substitute-in-file-name filename
1811  This function replaces environment variables references in  This function replaces environment variables references in
1812  @var{filename} with the environment variable values.  Following standard  @var{filename} with the environment variable values.  Following
1813  Unix shell syntax, @samp{$} is the prefix to substitute an environment  standard Unix shell syntax, @samp{$} is the prefix to substitute an
1814  variable value.  environment variable value.  If the input contains @samp{$$}, that is
1815    converted to @samp{$}; this gives the user a way to ``quote'' a
1816    @samp{$}.
1817    
1818  The environment variable name is the series of alphanumeric characters  The environment variable name is the series of alphanumeric characters
1819  (including underscores) that follow the @samp{$}.  If the character following  (including underscores) that follow the @samp{$}.  If the character following
1820  the @samp{$} is a @samp{@{}, then the variable name is everything up to the  the @samp{$} is a @samp{@{}, then the variable name is everything up to the
1821  matching @samp{@}}.  matching @samp{@}}.
1822    
1823    Calling @code{substitute-in-file-name} on output produced by
1824    @code{substitute-in-file-name} tends to give incorrect results.  For
1825    instance, use of @samp{$$} to quote a single @samp{$} won't work
1826    properly, and @samp{$} in an environment variable's value could lead
1827    to repeated substitution.  Therefore, programs that call this function
1828    and put the output where it will be passed to this function need to
1829    double all @samp{$} characters to prevent subsequent incorrect
1830    results.
1831    
1832  @c Wordy to avoid overfull hbox.  --rjc 15mar92  @c Wordy to avoid overfull hbox.  --rjc 15mar92
1833  Here we assume that the environment variable @code{HOME}, which holds  Here we assume that the environment variable @code{HOME}, which holds
1834  the user's home directory name, has value @samp{/xcssun/users/rms}.  the user's home directory name, has value @samp{/xcssun/users/rms}.

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