perror(2) [plan9 man page]

PERROR(2)							System Calls Manual							 PERROR(2)

NAME

       perror, syslog - system error messages

SYNOPSIS

       #include <u.h>
       #include <libc.h>

       void perror(char *s)

       void syslog(int cons, char *logname, char *fmt, ...)

DESCRIPTION

       Perror  produces a short error message on the standard error file describing the last error encountered during a call to the system.  First
       the argument string s is printed, then a colon, then the message and a newline.	If s is 0, only the error message and newline are printed.

       Syslog logs messages in the file named by logname in the directory /sys/log; the file must already exist and should be  append-only.   Log-
       name  must  contain no slashes.	The message is a line with several fields: the name of the machine writing the message; the date and time;
       the message specified by the print(2) format fmt and any following arguments; and a final newline.  If cons is set or the log  file  cannot
       be opened, the message is also printed on the system console.  Syslog can be used safely in multi-threaded programs.

SOURCE

       /sys/src/libc/port/perror.c
       /sys/src/libc/9sys/syslog.c

SEE ALSO

       intro(2), errstr(2), the %r format in print(2)

BUGS

       Perror is a holdover; the %r format in print(2) is preferred.

																	 PERROR(2)

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
       library function.  First (if s is not NULL and *s is not NUL) the argument 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 obtain the error message without the newline.  The largest message num-
       ber provided in the table is sys_nerr -1.  Be careful when directly accessing 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 perror() 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	because it internally used some other library function that failed.  Thus, if a failing call is not immediately followed by a call
       to perror, 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)