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All Rights Reserved 47 .\" 48 .TH WAIT 1 "May 17, 2020" 49 .SH NAME 50 wait \- await process completion 51 .SH SYNOPSIS 52 .nf 53 54 .fi 55 56 .SS "/bin/sh" 57 .nf 58 \fBwait\fR [\fIpid\fR]... 59 .fi 60 61 .SS "/bin/jsh /bin/ksh /usr/xpg4/bin/sh" 62 .nf 63 \fBwait\fR [\fIpid\fR]... 64 .fi 65 66 .LP 67 .nf 68 \fBwait\fR [% \fIjobid\fR...] 69 .fi 70 71 .SS "/bin/csh" 72 .nf 73 \fBwait\fR 74 .fi 75 76 .SS "ksh93" 77 .nf 78 \fBwait\fR [\fIjob...\fR] 79 .fi 80 81 .SH DESCRIPTION 82 The shell itself executes \fBwait\fR, without creating a new process. If you 83 get the error message \fBcannot fork,too many processes\fR, try using the 84 \fBwait\fR command to clean up your background processes. If this doesn't help, 85 the system process table is probably full or you have too many active 86 foreground processes. There is a limit to the number of process \fBID\fRs 87 associated with your login, and to the number the system can keep track of. 88 .sp 89 .LP 90 Not all the processes of a pipeline with three or more stages are children of 91 the shell, and thus cannot be waited for. 92 .SS "/bin/sh, /bin/jsh" 93 Wait for your background process whose process \fBID\fR is \fIpid\fR and report 94 its termination status. If \fIpid\fR is omitted, all your shell's currently 95 active background processes are waited for and the return code is \fB0\fR. The 96 \fBwait\fR utility accepts a job identifier, when Job Control is enabled (jsh), 97 and the argument, \fIjobid\fR, is preceded by a percent sign (\fB%\fR). 98 .sp 99 .LP 100 If \fIpid\fR is not an active process \fBID,\fR the \fBwait\fR utility returns 101 immediately and the return code is \fB0\fR. 102 .SS "csh" 103 Wait for your background processes. 104 .SS "ksh" 105 When an asynchronous list is started by the shell, the process \fBID\fR of the 106 last command in each element of the asynchronous list becomes known in the 107 current shell execution environment. 108 .sp 109 .LP 110 If the \fBwait\fR utility is invoked with no operands, it waits until all 111 process \fBIDs\fR known to the invoking shell have terminated and exit with an 112 exit status of \fB0\fR. 113 .sp 114 .LP 115 If one or more \fIpid\fR or \fIjobid\fR operands are specified that represent 116 known process \fBID\fRs (or jobids), the \fBwait\fR utility waits until all of 117 them have terminated. If one or more \fIpid\fR or \fIjobid\fR operands are 118 specified that represent unknown process \fBID\fRs (or jobids), \fBwait\fR 119 treats them as if they were known process \fBID\fRs (or jobids) that exited 120 with exit status \fB127\fR. The exit status returned by the \fBwait\fR utility 121 is the exit status of the process requested by the last \fIpid\fR or 122 \fIjobid\fR operand. 123 .sp 124 .LP 125 The known process \fBID\fRs are applicable only for invocations of \fBwait\fR 126 in the current shell execution environment. 127 .SS "ksh93" 128 wait with no operands, waits until all jobs known to the invoking shell have 129 terminated. If one or more job operands are specified, wait waits until all of 130 them have completed. Each job can be specified as one of the following: 131 .sp 132 .ne 2 133 .na 134 \fB\fInumber\fR\fR 135 .ad 136 .RS 12n 137 \fInumber\fR refers to a process ID. 138 .RE 139 140 .sp 141 .ne 2 142 .na 143 \fB\fB-\fR\fInumber\fR\fR 144 .ad 145 .RS 12n 146 \fInumber\fR refers to a process group ID. 147 .RE 148 149 .sp 150 .ne 2 151 .na 152 \fB\fB%\fR\fInumber\fR\fR 153 .ad 154 .RS 12n 155 \fInumber\fR refers to a job number 156 .RE 157 158 .sp 159 .ne 2 160 .na 161 \fB\fB%\fR\fIstring\fR\fR 162 .ad 163 .RS 12n 164 Refers to a job whose name begins with \fIstring\fR 165 .RE 166 167 .sp 168 .ne 2 169 .na 170 \fB\fB%?\fR\fIstring\fR\fR 171 .ad 172 .RS 12n 173 Refers to a job whose name contains \fIstring\fR 174 .RE 175 176 .sp 177 .ne 2 178 .na 179 \fB\fB%+\fR\fR 180 .ad 181 .br 182 .na 183 \fB\fB%%\fR\fR 184 .ad 185 .RS 12n 186 Refers to the current job 187 .RE 188 189 .sp 190 .ne 2 191 .na 192 \fB\fB%-\fR\fR 193 .ad 194 .RS 12n 195 Refers to the previous job 196 .RE 197 198 .sp 199 .LP 200 If one or more job operands is a process id or process group id not known by 201 the current shell environment, \fBwait\fR treats each of them as if it were a 202 process that exited with status 127. 203 .SH OPERANDS 204 The following operands are supported: 205 .sp 206 .ne 2 207 .na 208 \fB\fIpid\fR\fR 209 .ad 210 .RS 9n 211 The unsigned decimal integer process \fBID\fR of a command, for which the 212 utility is to wait for the termination. 213 .RE 214 215 .sp 216 .ne 2 217 .na 218 \fB\fIjobid\fR\fR 219 .ad 220 .RS 9n 221 A job control job \fBID\fR that identifies a background process group to be 222 waited for. The job control job \fBID\fR notation is applicable only for 223 invocations of \fBwait\fR in the current shell execution environment, and only 224 on systems supporting the job control option. 225 .RE 226 227 .SH USAGE 228 On most implementations, \fBwait\fR is a shell built-in. If it is called in a 229 subshell or separate utility execution environment, such as one of the 230 following, 231 .sp 232 .in +2 233 .nf 234 (wait) 235 nohup wait ... 236 find . -exec wait ... \e; 237 .fi 238 .in -2 239 .sp 240 241 .sp 242 .LP 243 it returns immediately because there is no known process \fBID\fRs to wait for 244 in those environments. 245 .SH EXAMPLES 246 \fBExample 1 \fRUsing A Script To Identify The Termination Signal 247 .sp 248 .LP 249 Although the exact value used when a process is terminated by a signal is 250 unspecified, if it is known that a signal terminated a process, a script can 251 still reliably figure out which signal is using \fBkill\fR, as shown by the 252 following (\fB/bin/ksh\fR and \fB/usr/xpg4/bin/sh\fR): 253 254 .sp 255 .in +2 256 .nf 257 sleep 1000& 258 pid=$! 259 kill -kill $pid 260 wait $pid 261 echo $pid was terminated by a SIG$(kill -l $(($?\(mi128))) signal. 262 .fi 263 .in -2 264 .sp 265 266 .LP 267 \fBExample 2 \fRReturning The Exit Status Of A Process 268 .sp 269 .LP 270 If the following sequence of commands is run in less than 31 seconds 271 (\fB/bin/ksh\fR and \fB/usr/xpg4/bin/sh\fR): 272 273 .sp 274 .in +2 275 .nf 276 sleep 257 | sleep 31 & 277 278 jobs -l %% 279 .fi 280 .in -2 281 .sp 282 283 .sp 284 .LP 285 then either of the following commands returns the exit status of the second 286 \fBsleep\fR in the pipeline: 287 288 .sp 289 .in +2 290 .nf 291 wait <\fIpid of sleep 31\fR> 292 wait %% 293 .fi 294 .in -2 295 .sp 296 297 .SH ENVIRONMENT VARIABLES 298 See \fBenviron\fR(5) for descriptions of the following environment variables 299 that affect the execution of \fBwait\fR: \fBLANG\fR, \fBLC_ALL\fR, 300 \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR. 301 .SH EXIT STATUS 302 .SS "ksh93" 303 The following exit values are returned by the \fBwait\fR built-in in 304 \fBksh93\fR: 305 .sp 306 .ne 2 307 .na 308 \fB\fB0\fR\fR 309 .ad 310 .RS 7n 311 \fBwait\fR was invoked with no operands. All processes known by the invoking 312 process have terminated. 313 .RE 314 315 .sp 316 .ne 2 317 .na 318 \fB\fB127\fR\fR 319 .ad 320 .RS 7n 321 \fIjob\fR is a process id or process group id that is unknown to the current 322 shell environment. 323 .RE 324 325 .SH ATTRIBUTES 326 See \fBattributes\fR(5) for descriptions of the following attributes: 327 .sp 328 329 .sp 330 .TS 331 box; 332 c | c 333 l | l . 334 ATTRIBUTE TYPE ATTRIBUTE VALUE 335 _ 336 Interface Stability Committed 337 _ 338 Standard See \fBstandards\fR(5). 339 .TE 340 341 .SH SEE ALSO 342 \fBcsh\fR(1), \fBjobs\fR(1), \fBksh\fR(1), \fBksh93\fR(1), \fBsh\fR(1), 343 \fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)