gen/FreeBSD/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 1.20 2004/10/04 14:04:37 jkoshy Exp $
  34 .\"
  35 .Dd March 6, 1999
  36 .Dt ERR 3
  37 .Os
  38 .Sh NAME
  39 .Nm err ,
  40 .Nm verr ,
  41 .Nm errc ,
  42 .Nm verrc ,
  43 .Nm errx ,
  44 .Nm verrx ,
  45 .Nm warn ,
  46 .Nm vwarn ,
  47 .Nm warnc ,
  48 .Nm vwarnc ,
  49 .Nm warnx ,
  50 .Nm vwarnx ,
  51 .Nm err_set_exit ,
  52 .Nm err_set_file
  53 .Nd formatted error messages
  54 .Sh LIBRARY
  55 .Lb libc
  56 .Sh SYNOPSIS
  57 .In err.h
  58 .Ft void
  59 .Fn err "int eval" "const char *fmt" "..."
  60 .Ft void
  61 .Fn err_set_exit "void (*exitf)(int)"
  62 .Ft void
  63 .Fn err_set_file "void *vfp"
  64 .Ft void
  65 .Fn errc "int eval" "int code" "const char *fmt" "..."
  66 .Ft void
  67 .Fn errx "int eval" "const char *fmt" "..."
  68 .Ft void
  69 .Fn warn "const char *fmt" "..."
  70 .Ft void
  71 .Fn warnc "int code" "const char *fmt" "..."
  72 .Ft void
  73 .Fn warnx "const char *fmt" "..."
  74 .In stdarg.h
  75 .Ft void
  76 .Fn verr "int eval" "const char *fmt" "va_list args"
  77 .Ft void
  78 .Fn verrc "int eval" "int code" "const char *fmt" "va_list args"
  79 .Ft void
  80 .Fn verrx "int eval" "const char *fmt" "va_list args"
  81 .Ft void
  82 .Fn vwarn "const char *fmt" "va_list args"
  83 .Ft void
  84 .Fn vwarnc "int code" "const char *fmt" "va_list args"
  85 .Ft void
  86 .Fn vwarnx "const char *fmt" "va_list args"
  87 .Sh DESCRIPTION
  88 The
  89 .Fn err
  90 and
  91 .Fn warn
  92 family of functions display a formatted error message on the standard
  93 error output, or on another file specified using the
  94 .Fn err_set_file
  95 function.
  96 In all cases, the last component of the program name, a colon character,
  97 and a space are output.
  98 If the
  99 .Fa fmt
 100 argument is not NULL, the
 101 .Xr printf 3
 102 -like formatted error message is output.
 103 The output is terminated by a newline character.
 104 .Pp
 105 The
 106 .Fn err ,
 107 .Fn errc ,
 108 .Fn verr ,
 109 .Fn verrc ,
 110 .Fn warn ,
 111 .Fn warnc ,
 112 .Fn vwarn ,
 113 and
 114 .Fn vwarnc
 115 functions append an error message obtained from
 116 .Xr strerror 3
 117 based on a code or the global variable
 118 .Va errno ,
 119 preceded by another colon and space unless the
 120 .Fa fmt
 121 argument is
 122 .Dv NULL .
 123 .Pp
 124 In the case of the
 125 .Fn errc ,
 126 .Fn verrc ,
 127 .Fn warnc ,
 128 and
 129 .Fn vwarnc
 130 functions,
 131 the
 132 .Fa code
 133 argument is used to look up the error message.
 134 .Pp
 135 The
 136 .Fn err ,
 137 .Fn verr ,
 138 .Fn warn ,
 139 and
 140 .Fn vwarn
 141 functions use the global variable
 142 .Va errno
 143 to look up the error message.
 144 .Pp
 145 The
 146 .Fn errx
 147 and
 148 .Fn warnx
 149 functions do not append an error message.
 150 .Pp
 151 The
 152 .Fn err ,
 153 .Fn verr ,
 154 .Fn errc ,
 155 .Fn verrc ,
 156 .Fn errx ,
 157 and
 158 .Fn verrx
 159 functions do not return, but exit with the value of the argument
 160 .Fa eval .
 161 It is recommended that the standard values defined in
 162 .Xr sysexits 3
 163 be used for the value of
 164 .Fa eval .
 165 The
 166 .Fn err_set_exit
 167 function can be used to specify a function which is called before
 168 .Xr exit 3
 169 to perform any necessary cleanup; passing a null function pointer for
 170 .Va exitf
 171 resets the hook to do nothing.
 172 The
 173 .Fn err_set_file
 174 function sets the output stream used by the other functions.
 175 Its
 176 .Fa vfp
 177 argument must be either a pointer to an open stream
 178 (possibly already converted to void *)
 179 or a null pointer
 180 (in which case the output stream is set to standard error).
 181 .Sh EXAMPLES
 182 Display the current errno information string and exit:
 183 .Bd -literal -offset indent
 184 if ((p = malloc(size)) == NULL)
 185         err(1, NULL);
 186 if ((fd = open(file_name, O_RDONLY, 0)) == -1)
 187         err(1, "%s", file_name);
 188 .Ed
 189 .Pp
 190 Display an error message and exit:
 191 .Bd -literal -offset indent
 192 if (tm.tm_hour < START_TIME)
 193         errx(1, "too early, wait until %s", start_time_string);
 194 .Ed
 195 .Pp
 196 Warn of an error:
 197 .Bd -literal -offset indent
 198 if ((fd = open(raw_device, O_RDONLY, 0)) == -1)
 199         warnx("%s: %s: trying the block device",
 200             raw_device, strerror(errno));
 201 if ((fd = open(block_device, O_RDONLY, 0)) == -1)
 202         err(1, "%s", block_device);
 203 .Ed
 204 .Pp
 205 Warn of an error without using the global variable
 206 .Va errno :
 207 .Bd -literal -offset indent
 208 error = my_function();  /* returns a value from <errno.h> */
 209 if (error != 0)
 210         warnc(error, "my_function");
 211 .Ed
 212 .Sh SEE ALSO
 213 .Xr exit 3 ,
 214 .Xr fmtmsg 3 ,
 215 .Xr printf 3 ,
 216 .Xr strerror 3 ,
 217 .Xr sysexits 3
 218 .Sh HISTORY
 219 The
 220 .Fn err
 221 and
 222 .Fn warn
 223 functions first appeared in
 224 .Bx 4.4 .
 225 The
 226 .Fn err_set_exit
 227 and
 228 .Fn err_set_file
 229 functions first appeared in
 230 .Fx 2.1 .
 231 The
 232 .Fn errc
 233 and
 234 .Fn warnc
 235 functions first appeared in
 236 .Fx 3.0 .