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Diffstat (limited to 'Doc/help/wait')
| -rw-r--r-- | Doc/help/wait | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/Doc/help/wait b/Doc/help/wait new file mode 100644 index 000000000..876a9669f --- /dev/null +++ b/Doc/help/wait @@ -0,0 +1,25 @@ +wait [ job ... ] + Wait for the specified jobs or processes. If job is not given + then all currently active child processes are waited for. Each + job can be either a job specification or the process ID of a job + in the job table. The exit status from this command is that of + the job waited for. If job represents an unknown job or process + ID, a warning is printed (unless the POSIX_BUILTINS option is + set) and the exit status is 127. + + It is possible to wait for recent processes (specified by + process ID, not by job) that were running in the background even + if the process has exited. Typically the process ID will be + recorded by capturing the value of the variable $! immediately + after the process has been started. There is a limit on the + number of process IDs remembered by the shell; this is given by + the value of the system configuration parameter CHILD_MAX. When + this limit is reached, older process IDs are discarded, least + recently started processes first. + + Note there is no protection against the process ID wrapping, + i.e. if the wait is not executed soon enough there is a chance + the process waited for is the wrong one. A conflict implies + both process IDs have been generated by the shell, as other pro- + cesses are not recorded, and that the user is potentially inter- + ested in both, so this problem is intrinsic to process IDs. |