1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" From: @(#)err.3 8.1 (Berkeley) 6/9/93 29.\" $FreeBSD$ 30.\" 31.Dd March 29, 2012 32.Dt ERR 3 33.Os 34.Sh NAME 35.Nm err , 36.Nm verr , 37.Nm errc , 38.Nm verrc , 39.Nm errx , 40.Nm verrx , 41.Nm warn , 42.Nm vwarn , 43.Nm warnc , 44.Nm vwarnc , 45.Nm warnx , 46.Nm vwarnx , 47.Nm err_set_exit , 48.Nm err_set_file 49.Nd formatted error messages 50.Sh LIBRARY 51.Lb libc 52.Sh SYNOPSIS 53.In err.h 54.Ft void 55.Fn err "int eval" "const char *fmt" "..." 56.Ft void 57.Fn err_set_exit "void (*exitf)(int)" 58.Ft void 59.Fn err_set_file "void *vfp" 60.Ft void 61.Fn errc "int eval" "int code" "const char *fmt" "..." 62.Ft void 63.Fn errx "int eval" "const char *fmt" "..." 64.Ft void 65.Fn warn "const char *fmt" "..." 66.Ft void 67.Fn warnc "int code" "const char *fmt" "..." 68.Ft void 69.Fn warnx "const char *fmt" "..." 70.In stdarg.h 71.Ft void 72.Fn verr "int eval" "const char *fmt" "va_list args" 73.Ft void 74.Fn verrc "int eval" "int code" "const char *fmt" "va_list args" 75.Ft void 76.Fn verrx "int eval" "const char *fmt" "va_list args" 77.Ft void 78.Fn vwarn "const char *fmt" "va_list args" 79.Ft void 80.Fn vwarnc "int code" "const char *fmt" "va_list args" 81.Ft void 82.Fn vwarnx "const char *fmt" "va_list args" 83.Sh DESCRIPTION 84The 85.Fn err 86and 87.Fn warn 88family of functions display a formatted error message on the standard 89error output, or on another file specified using the 90.Fn err_set_file 91function. 92In all cases, the last component of the program name, a colon character, 93and a space are output. 94If the 95.Fa fmt 96argument is not NULL, the 97.Xr printf 3 Ns 98-like formatted error message is output. 99The output is terminated by a newline character. 100.Pp 101The 102.Fn err , 103.Fn errc , 104.Fn verr , 105.Fn verrc , 106.Fn warn , 107.Fn warnc , 108.Fn vwarn , 109and 110.Fn vwarnc 111functions append an error message obtained from 112.Xr strerror 3 113based on a supplied error code value or the global variable 114.Va errno , 115preceded by another colon and space unless the 116.Fa fmt 117argument is 118.Dv NULL . 119.Pp 120In the case of the 121.Fn errc , 122.Fn verrc , 123.Fn warnc , 124and 125.Fn vwarnc 126functions, 127the 128.Fa code 129argument is used to look up the error message. 130.Pp 131The 132.Fn err , 133.Fn verr , 134.Fn warn , 135and 136.Fn vwarn 137functions use the global variable 138.Va errno 139to look up the error message. 140.Pp 141The 142.Fn errx 143and 144.Fn warnx 145functions do not append an error message. 146.Pp 147The 148.Fn err , 149.Fn verr , 150.Fn errc , 151.Fn verrc , 152.Fn errx , 153and 154.Fn verrx 155functions do not return, but exit with the value of the argument 156.Fa eval . 157It is recommended that the standard values defined in 158.Xr sysexits 3 159be used for the value of 160.Fa eval . 161The 162.Fn err_set_exit 163function can be used to specify a function which is called before 164.Xr exit 3 165to perform any necessary cleanup; passing a null function pointer for 166.Va exitf 167resets the hook to do nothing. 168The 169.Fn err_set_file 170function sets the output stream used by the other functions. 171Its 172.Fa vfp 173argument must be either a pointer to an open stream 174(possibly already converted to void *) 175or a null pointer 176(in which case the output stream is set to standard error). 177.Sh EXAMPLES 178Display the current errno information string and exit: 179.Bd -literal -offset indent 180if ((p = malloc(size)) == NULL) 181 err(EX_OSERR, NULL); 182if ((fd = open(file_name, O_RDONLY, 0)) == -1) 183 err(EX_NOINPUT, "%s", file_name); 184.Ed 185.Pp 186Display an error message and exit: 187.Bd -literal -offset indent 188if (tm.tm_hour < START_TIME) 189 errx(EX_DATAERR, "too early, wait until %s", 190 start_time_string); 191.Ed 192.Pp 193Warn of an error: 194.Bd -literal -offset indent 195if ((fd = open(raw_device, O_RDONLY, 0)) == -1) 196 warnx("%s: %s: trying the block device", 197 raw_device, strerror(errno)); 198if ((fd = open(block_device, O_RDONLY, 0)) == -1) 199 err(EX_OSFILE, "%s", block_device); 200.Ed 201.Pp 202Warn of an error without using the global variable 203.Va errno : 204.Bd -literal -offset indent 205error = my_function(); /* returns a value from <errno.h> */ 206if (error != 0) 207 warnc(error, "my_function"); 208.Ed 209.Sh SEE ALSO 210.Xr exit 3 , 211.Xr fmtmsg 3 , 212.Xr printf 3 , 213.Xr strerror 3 , 214.Xr sysexits 3 215.Sh STANDARDS 216The 217.Fn err 218and 219.Fn warn 220families of functions are 221.Bx 222extensions. 223As such they should not be used in truly portable code. 224Use 225.Fn strerror 226or similar functions instead. 227.Sh HISTORY 228The 229.Fn err 230and 231.Fn warn 232functions first appeared in 233.Bx 4.4 . 234The 235.Fn err_set_exit 236and 237.Fn err_set_file 238functions first appeared in 239.Fx 2.1 . 240The 241.Fn errc 242and 243.Fn warnc 244functions first appeared in 245.Fx 3.0 . 246