plan9 man page for errstr

ERRSTR(2)							System Calls Manual							 ERRSTR(2)

NAME
       errstr, werrstr - description of last system call error

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

       int errstr(char *err)

       void werrstr(char *fmt, ...)

DESCRIPTION
       When  a	system	call  fails it returns -1 and records a string describing the error in a per-process buffer.  Errstr swaps the contents of
       that buffer with the contents of the array err.	Err should contain at least ERRLEN characters (defined in <libc.h>).  Usually errstr  will
       be  called  with an empty string, but the exchange property provides a mechanism for libraries to set the return value for the next call to
       errstr.

       If no system call has generated an error since the last call to errstr with an empty string, the result is an empty string.

       The verb r in print(2) calls errstr and outputs the error string.

       Werrstr takes a print style format as its argument and uses it to format a string to pass to errstr.  The string returned  from	errstr	is
       discarded.

SOURCE
       /sys/src/libc/9syscall
       /sys/src/libc/9sys/werrstr.c

DIAGNOSTICS
       Errstr always returns 0.

SEE ALSO
       intro(2), perror(2)

																	 ERRSTR(2)