man.postnix Miscellaneous man pages of Plan 9 related material

     ERRSTR(2)                                               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)

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