man3/err.3

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  32 .\"     From: @(#)err.3 8.1 (Berkeley) 6/9/93
  33 .\" $FreeBSD: src/lib/libc/gen/err.3,v 1.11.2.5 2001/08/17 15:42:32 ru Exp $
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  35 .Dd March 6, 1999
  36 .Dt ERR 3
  37 .Os
  38 .Sh NAME
  39 .Nm err ,
  40 .Nm verr ,
  41 .Nm errx ,
  42 .Nm verrx ,
  43 .Nm warn ,
  44 .Nm vwarn ,
  45 .Nm warnx ,
  46 .Nm vwarnx ,
  47 .Nd formatted error messages
  48 .Sh SYNOPSIS
  49 .Fd #include <err.h>
  50 .Ft void
  51 .Fn err "int eval" "const char *fmt" "..."
  52 .Ft void
  53 .Fn errx "int eval" "const char *fmt" "..."
  54 .Ft void
  55 .Fn warn "const char *fmt" "..."
  56 .Ft void
  57 .Fn warnx "const char *fmt" "..."
  58 .Fd #include <stdarg.h>
  59 .Ft void
  60 .Fn verr "int eval" "const char *fmt" "va_list args"
  61 .Ft void
  62 .Fn verrx "int eval" "const char *fmt" "va_list args"
  63 .Ft void
  64 .Fn vwarn "const char *fmt" "va_list args"
  65 .Ft void
  66 .Fn vwarnx "const char *fmt" "va_list args"
  67 .Sh DESCRIPTION
  68 The
  69 .Fn err
  70 and
  71 .Fn warn
  72 family of functions display a formatted error message on the standard
  73 error output.
  74 In all cases, the last component of the program name, a colon character,
  75 and a space are output.
  76 If the
  77 .Fa fmt
  78 argument is not NULL, the
  79 .Xr printf 3
  80 -like formatted error message is output.
  81 The output is terminated by a newline character.
  82 .Pp
  83 The
  84 .Fn err ,
  85 .Fn verr ,
  86 .Fn warn ,
  87 and
  88 .Fn vwarn
  89 functions append an error message obtained from
  90 .Xr strerror 3
  91 based on a code or the global variable
  92 .Va errno ,
  93 preceded by another colon and space unless the
  94 .Fa fmt
  95 argument is
  96 .Dv NULL .
  97 .Pp
  98 The
  99 .Fn err ,
 100 .Fn verr ,
 101 .Fn warn ,
 102 and
 103 .Fn vwarn
 104 functions use the global variable
 105 .Va errno
 106 to look up the error message.
 107 .Pp
 108 The
 109 .Fn errx
 110 and
 111 .Fn warnx
 112 functions do not append an error message.
 113 .Pp
 114 The
 115 .Fn err ,
 116 .Fn verr ,
 117 .Fn errx ,
 118 and
 119 .Fn verrx
 120 functions do not return, but exit with the value of the argument
 121 .Fa eval .
 122 .Sh EXAMPLES
 123 Display the current errno information string and exit:
 124 .Bd -literal -offset indent
 125 if ((p = malloc(size)) == NULL)
 126         err(1, NULL);
 127 if ((fd = open(file_name, O_RDONLY, 0)) == \-1)
 128         err(1, "%s", file_name);
 129 .Ed
 130 .Pp
 131 Display an error message and exit:
 132 .Bd -literal -offset indent
 133 if (tm.tm_hour < START_TIME)
 134         errx(1, "too early, wait until %s", start_time_string);
 135 .Ed
 136 .Pp
 137 Warn of an error:
 138 .Bd -literal -offset indent
 139 if ((fd = open(raw_device, O_RDONLY, 0)) == \-1)
 140         warnx("%s: %s: trying the block device",
 141             raw_device, strerror(errno));
 142 if ((fd = open(block_device, O_RDONLY, 0)) == \-1)
 143         err(1, "%s", block_device);
 144 .Ed
 145 .Sh SEE ALSO
 146 .Xr exit 3 ,
 147 .Xr printf 3 ,
 148 .Xr perror 3 ,
 149 .Xr strerror 3
 150 .Sh "CONFORMING TO"
 151 These functions are non-standard BSD extensions.
 152 .Sh HISTORY
 153 The
 154 .Fn err
 155 and
 156 .Fn warn
 157 functions first appeared in
 158 .Bx 4.4 .