kc3-lang/libbsd/man/setmode.3bsd

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  man: Lowercase man page title While using fully uppercase man page titles has been the usual convention for a very long time, it is rather ugly and something that some other projects are switching away from.

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• man/setmode.3bsd

• .\"	$NetBSD: setmode.3,v 1.18.28.1 2009/01/04 17:02:19 christos Exp $
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  .\"     @(#)setmode.3	8.2 (Berkeley) 4/28/95
  .\" $FreeBSD: src/lib/libc/gen/setmode.3,v 1.12 2007/01/09 00:27:55 imp Exp $
  .\"
  .Dd January 4, 2009
  .Dt setmode 3bsd
  .Os
  .Sh NAME
  .Nm getmode ,
  .Nm setmode
  .Nd modify mode bits
  .Sh LIBRARY
  .ds str-Lb-libbsd Utility functions from BSD systems (libbsd, \-lbsd)
  .ds doc-str-Lb-libbsd \*[str-Lb-libbsd]
  .Lb libbsd
  .Sh SYNOPSIS
  .In unistd.h
  (See
  .Xr libbsd 7
  for include usage.)
  .Ft void *
  .Fn setmode "const char *mode_str"
  .Ft mode_t
  .Fn getmode "const void *set" "mode_t mode"
  .Sh DESCRIPTION
  The
  .Fn setmode
  function accepts a string representation of a file mode change,
  compiles it to binary form, and returns an abstract representation
  that may be passed to
  .Fn getmode .
  The string may be an numeric (octal) or symbolic string of the form
  accepted by
  .Xr chmod 1 ,
  and may represent either an exact mode to set or a change to make to
  the existing mode.
  .Pp
  The
  .Fn getmode
  function
  adjusts the file permission bits given by
  .Fa mode
  according to the compiled change representation
  .Fa set ,
  and returns the adjusted mode.
  While only the permission bits are altered, other parts of the file
  mode, particularly the type, may be examined.
  .Pp
  Because some of the possible symbolic values are defined relative to
  the file creation mask,
  .Fn setmode
  may call
  .Xr umask 2 ,
  temporarily changing the mask.
  If this occurs, the file creation mask will be restored before
  .Fn setmode
  returns.
  If the calling program changes the value of its file creation mask
  after calling
  .Fn setmode ,
  .Fn setmode
  must be called again to recompile the mode string if
  .Fn getmode
  is to modify future file modes correctly.
  .Pp
  If the mode passed to
  .Fn setmode
  is invalid,
  .Fn setmode
  returns
  .Dv NULL .
  .Pp
  The value returned from
  .Fn setmode
  is obtained from
  .Fn malloc
  and should be returned to the system with
  .Fn free
  when the program is done with it, generally after a call to
  .Fn getmode .
  .Sh EXAMPLES
  The effects of the shell command
  .Ql "chmod a+x myscript.sh"
  can be duplicated as follows:
  .Bd -literal -offset indent
  const char *file = "myscript.sh";
  struct stat st;
  mode_t newmode;
  
  stat(file, \*[Am]st);
  newmode = getmode(setmode("a+x"), st.st_mode);
  chmod(file, newmode);
  .Ed
  .Sh ERRORS
  The
  .Fn setmode
  function
  may fail and set
  .Va errno
  for any of the errors specified for the library routines
  .Xr malloc 3
  or
  .Xr strtol 3 .
  In addition,
  .Fn setmode
  will fail and set
  .Va errno
  to:
  .Bl -tag -width Er
  .It Bq Er EINVAL
  The
  .Fa mode
  argument does not represent a valid mode.
  .El
  .Sh SEE ALSO
  .Xr chmod 1 ,
  .Xr stat 2 ,
  .Xr umask 2 ,
  .Xr malloc 3
  .Sh HISTORY
  The
  .Fn getmode
  and
  .Fn setmode
  functions first appeared in
  .Bx 4.4 .
  .Sh BUGS
  The type of
  .Fa set
  should really be some opaque struct type used only by these functions
  rather than
  .Ft void * .
  

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