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All Rights Reserved 47 .\" 48 .TH WAIT 1 "Mar 13, 2008" 49 .SH NAME 50 wait \- await process completion 51 .SH SYNOPSIS 52 .LP 53 .nf 54 55 .fi 56 57 .SS "/bin/sh" 58 .LP 59 .nf 60 \fBwait\fR [\fIpid\fR]... 61 .fi 62 63 .SS "/bin/jsh /bin/ksh /usr/xpg4/bin/sh" 64 .LP 65 .nf 66 \fBwait\fR [\fIpid\fR]... 67 .fi 68 69 .LP 70 .nf 71 \fBwait\fR [% \fIjobid\fR...] 72 .fi 73 74 .SS "/bin/csh" 75 .LP 76 .nf 77 \fBwait\fR 78 .fi 79 80 .SS "ksh93" 81 .LP 82 .nf 83 \fBwait\fR [\fIjob...\fR] 84 .fi 85 86 .SH DESCRIPTION 87 .sp 88 .LP 89 The shell itself executes \fBwait\fR, without creating a new process. If you 90 get the error message \fBcannot fork,too many processes\fR, try using the 91 \fBwait\fR command to clean up your background processes. If this doesn't help, 92 the system process table is probably full or you have too many active 93 foreground processes. There is a limit to the number of process \fBID\fRs 94 associated with your login, and to the number the system can keep track of. 95 .sp 96 .LP 97 Not all the processes of a pipeline with three or more stages are children of 98 the shell, and thus cannot be waited for. 99 .SS "/bin/sh, /bin/jsh" 100 .sp 101 .LP 102 Wait for your background process whose process \fBID\fR is \fIpid\fR and report 103 its termination status. If \fIpid\fR is omitted, all your shell's currently 104 active background processes are waited for and the return code is \fB0\fR. The 105 \fBwait\fR utility accepts a job identifier, when Job Control is enabled (jsh), 106 and the argument, \fIjobid\fR, is preceded by a percent sign (\fB%\fR). 107 .sp 108 .LP 109 If \fIpid\fR is not an active process \fBID,\fR the \fBwait\fR utility returns 110 immediately and the return code is \fB0\fR. 111 .SS "csh" 112 .sp 113 .LP 114 Wait for your background processes. 115 .SS "ksh" 116 .sp 117 .LP 118 When an asynchronous list is started by the shell, the process \fBID\fR of the 119 last command in each element of the asynchronous list becomes known in the 120 current shell execution environment. 121 .sp 122 .LP 123 If the \fBwait\fR utility is invoked with no operands, it waits until all 124 process \fBIDs\fR known to the invoking shell have terminated and exit with an 125 exit status of \fB0\fR. 126 .sp 127 .LP 128 If one or more \fIpid\fR or \fIjobid\fR operands are specified that represent 129 known process \fBID\fRs (or jobids), the \fBwait\fR utility waits until all of 130 them have terminated. If one or more \fIpid\fR or \fIjobid\fR operands are 131 specified that represent unknown process \fBID\fRs (or jobids), \fBwait\fR 132 treats them as if they were known process \fBID\fRs (or jobids) that exited 133 with exit status \fB127\fR. The exit status returned by the \fBwait\fR utility 134 is the exit status of the process requested by the last \fIpid\fR or 135 \fIjobid\fR operand. 136 .sp 137 .LP 138 The known process \fBID\fRs are applicable only for invocations of \fBwait\fR 139 in the current shell execution environment. 140 .SS "ksh93" 141 .sp 142 .LP 143 wait with no operands, waits until all jobs known to the invoking shell have 144 terminated. If one or more job operands are specified, wait waits until all of 145 them have completed. Each job can be specified as one of the following: 146 .sp 147 .ne 2 148 .na 149 \fB\fInumber\fR\fR 150 .ad 151 .RS 12n 152 \fInumber\fR refers to a process ID. 153 .RE 154 155 .sp 156 .ne 2 157 .na 158 \fB\fB-\fR\fInumber\fR\fR 159 .ad 160 .RS 12n 161 \fInumber\fR refers to a process group ID. 162 .RE 163 164 .sp 165 .ne 2 166 .na 167 \fB\fB%\fR\fInumber\fR\fR 168 .ad 169 .RS 12n 170 \fInumber\fR refers to a job number 171 .RE 172 173 .sp 174 .ne 2 175 .na 176 \fB\fB%\fR\fIstring\fR\fR 177 .ad 178 .RS 12n 179 Refers to a job whose name begins with \fIstring\fR 180 .RE 181 182 .sp 183 .ne 2 184 .na 185 \fB\fB%?\fR\fIstring\fR\fR 186 .ad 187 .RS 12n 188 Refers to a job whose name contains \fIstring\fR 189 .RE 190 191 .sp 192 .ne 2 193 .na 194 \fB\fB%+\fR\fR 195 .ad 196 .br 197 .na 198 \fB\fB%%\fR\fR 199 .ad 200 .RS 12n 201 Refers to the current job 202 .RE 203 204 .sp 205 .ne 2 206 .na 207 \fB\fB%-\fR\fR 208 .ad 209 .RS 12n 210 Refers to the previous job 211 .RE 212 213 .sp 214 .LP 215 If one ore more job operands is a process id or process group id not known by 216 the current shell environment, \fBwait\fR treats each of them as if it were a 217 process that exited with status 127. 218 .SH OPERANDS 219 .sp 220 .LP 221 The following operands are supported: 222 .sp 223 .ne 2 224 .na 225 \fB\fIpid\fR\fR 226 .ad 227 .RS 9n 228 The unsigned decimal integer process \fBID\fR of a command, for which the 229 utility is to wait for the termination. 230 .RE 231 232 .sp 233 .ne 2 234 .na 235 \fB\fIjobid\fR\fR 236 .ad 237 .RS 9n 238 A job control job \fBID\fR that identifies a background process group to be 239 waited for. The job control job \fBID\fR notation is applicable only for 240 invocations of \fBwait\fR in the current shell execution environment, and only 241 on systems supporting the job control option. 242 .RE 243 244 .SH USAGE 245 .sp 246 .LP 247 On most implementations, \fBwait\fR is a shell built-in. If it is called in a 248 subshell or separate utility execution environment, such as one of the 249 following, 250 .sp 251 .in +2 252 .nf 253 (wait) 254 nohup wait ... 255 find . -exec wait ... \e; 256 .fi 257 .in -2 258 .sp 259 260 .sp 261 .LP 262 it returns immediately because there is no known process \fBID\fRs to wait for 263 in those environments. 264 .SH EXAMPLES 265 .LP 266 \fBExample 1 \fRUsing A Script To Identify The Termination Signal 267 .sp 268 .LP 269 Although the exact value used when a process is terminated by a signal is 270 unspecified, if it is known that a signal terminated a process, a script can 271 still reliably figure out which signal is using \fBkill\fR, as shown by the 272 following (\fB/bin/ksh\fR and \fB/usr/xpg4/bin/sh\fR): 273 274 .sp 275 .in +2 276 .nf 277 sleep 1000& 278 pid=$! 279 kill -kill $pid 280 wait $pid 281 echo $pid was terminated by a SIG$(kill -l $(($?\(mi128))) signal. 282 .fi 283 .in -2 284 .sp 285 286 .LP 287 \fBExample 2 \fRReturning The Exit Status Of A Process 288 .sp 289 .LP 290 If the following sequence of commands is run in less than 31 seconds 291 (\fB/bin/ksh\fR and \fB/usr/xpg4/bin/sh\fR): 292 293 .sp 294 .in +2 295 .nf 296 sleep 257 | sleep 31 & 297 298 jobs -l %% 299 .fi 300 .in -2 301 .sp 302 303 .sp 304 .LP 305 then either of the following commands returns the exit status of the second 306 \fBsleep\fR in the pipeline: 307 308 .sp 309 .in +2 310 .nf 311 wait <\fIpid of sleep 31\fR> 312 wait %% 313 .fi 314 .in -2 315 .sp 316 317 .SH ENVIRONMENT VARIABLES 318 .sp 319 .LP 320 See \fBenviron\fR(5) for descriptions of the following environment variables 321 that affect the execution of \fBwait\fR: \fBLANG\fR, \fBLC_ALL\fR, 322 \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR. 323 .SH EXIT STATUS 324 .SS "ksh93" 325 .sp 326 .LP 327 The following exit values are returned by the \fBwait\fR built-in in 328 \fBksh93\fR: 329 .sp 330 .ne 2 331 .na 332 \fB\fB0\fR\fR 333 .ad 334 .RS 7n 335 \fBwait\fR was invoked with no operands. All processes known by the invoking 336 process have terminated. 337 .RE 338 339 .sp 340 .ne 2 341 .na 342 \fB\fB127\fR\fR 343 .ad 344 .RS 7n 345 \fIjob\fR is a process id or process group id that is unknown to the current 346 shell environment. 347 .RE 348 349 .SH ATTRIBUTES 350 .sp 351 .LP 352 See \fBattributes\fR(5) for descriptions of the following attributes: 353 .sp 354 355 .sp 356 .TS 357 box; 358 c | c 359 l | l . 360 ATTRIBUTE TYPE ATTRIBUTE VALUE 361 _ 362 Interface Stability Committed 363 _ 364 Standard See \fBstandards\fR(5). 365 .TE 366 367 .SH SEE ALSO 368 .sp 369 .LP 370 \fBcsh\fR(1), \fBjobs\fR(1), \fBksh\fR(1), \fBksh93\fR(1), \fBsh\fR(1), 371 \fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)