ref: a5db044fd3ccb8f021d4deb07b3dc732ed41d699
dir: /sys/man/2/errstr/
.TH ERRSTR 2 .SH NAME errstr, rerrstr, werrstr \- description of last system call error .SH SYNOPSIS .B #include <u.h> .br .B #include <libc.h> .PP .B int errstr(char *err, uint nerr) .PP .B void rerrstr(char *err, uint nerr) .PP .B void werrstr(char *fmt, ...) .SH DESCRIPTION When a system call fails it returns \-1 and records a null terminated string describing the error in a per-process buffer. .I Errstr swaps the contents of that buffer with the contents of the array .IR err . .I Errstr will write at most .I nerr bytes into .IR 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 .I 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 .IR errstr . .PP The per-process buffer is .B ERRMAX bytes long. Any error string provided by the user will be truncated at .B ERRMAX-1 bytes. .B ERRMAX is defined in .BR <libc.h> . .PP If no system call has generated an error since the last call to .I errstr with an empty string, the result is an empty string. .PP The verb .B r in .IR print (2) calls .I errstr and outputs the error string. .PP .I Rerrstr reads the error string but does not modify the per-process buffer, so a subsequent .I errstr will recover the same string. .PP .I Werrstr takes a .I print style format as its argument and uses it to format a string to pass to .IR errstr . The string returned from .I errstr is discarded. .SH SOURCE .B /sys/src/libc/9syscall .br .B /sys/src/libc/9sys/rerrstr.c .br .B /sys/src/libc/9sys/werrstr.c .SH DIAGNOSTICS .I Errstr always returns 0. .SH SEE ALSO .IR intro (2), .IR perror (2)