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PERROR(3)		       Library functions		     PERROR(3)

NAME
       perror -	print a	system error message

SYNOPSIS
       #include	<stdio.h>

       void perror(const char *s);

       #include	<errno.h>

       const char *sys_errlist[];
       int sys_nerr;

DESCRIPTION
       The  routine  perror() produces a message on the	standard error output,
       describing the last error encountered during a call to a	system or  li-
       brary  function.	  First	(if s is not NULL and *s is not	NUL) the argu-
       ment string s is	printed, followed by a colon and a  blank.   Then  the
       message and a new-line.

       To  be  of most use, the	argument string	should include the name	of the
       function	that incurred the error.  The error number is taken  from  the
       external	variable errno,	which is set when errors occur but not cleared
       when non-erroneous calls	are made.

       The global error	list sys_errlist[] indexed by errno can	be used	to ob-
       tain the	error message without the newline.  The	largest	message	number
       provided	in the table is	sys_nerr -1.  Be careful when directly access-
       ing  this  list	because	 new  error  values may	not have been added to
       sys_errlist[].

       When a system call fails, it usually returns -1 and sets	 the  variable
       errno to	a value	describing what	went wrong. (These values can be found
       in _errno.h_.)  Many library functions do likewise.  The	function  per-
       ror()  serves  to  translate  this error	code into human-readable form.
       Note that errno is undefined after a successful library call: this call
       may well	change this variable, even though it succeeds, for example be-
       cause it	internally used	 some  other  library  function	 that  failed.
       Thus,  if  a failing call is not	immediately followed by	a call to per-
       ror, the	value of errno should be saved.

CONFORMING TO
       ANSI C, BSD 4.3,	POSIX, X/OPEN

SEE ALSO
       strerror(3)

				  2001-12-14			     PERROR(3)

NAME | SYNOPSIS | DESCRIPTION | CONFORMING TO | SEE ALSO

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