ERRSTR(2) ERRSTR(2)
NAME
errstr, rerrstr, werrstr - description of last system call
error
SYNOPSIS
#include <u.h>
#include <libc.h>
int errstr(char *err, uint nerr)
void rerrstr(char *err, uint nerr)
void werrstr(char *fmt, ...)
DESCRIPTION
When a system call fails it returns -1 and records a null
terminated string describing the error in a per-process
buffer. Errstr swaps the contents of that buffer with the
contents of the array err. Errstr will write at most nerr
bytes into err; if the per-process error string does not
fit, it is silently truncated at a UTF character boundary.
The returned string is NUL-terminated. 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.
The per-process buffer is ERRMAX bytes long. Any error
string provided by the user will be truncated at ERRMAX-1
bytes. ERRMAX is defined in <libc.h>.
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.
Rerrstr reads the error string but does not modify the per-
process buffer, so a subsequent errstr will recover the same
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
Page 1 Plan 9 (printed 12/21/24)
ERRSTR(2) ERRSTR(2)
Errstr always returns 0.
SEE ALSO
intro(2), perror(2)
Page 2 Plan 9 (printed 12/21/24)