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 12/29/24) ERRSTR(2) ERRSTR(2) Errstr always returns 0. SEE ALSO intro(2), perror(2) Page 2 Plan 9 (printed 12/29/24)