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WHEN(1) NAME when - repeatedly runs a command, then another when the first succeeds SYNOPSIS when [-n <seconds>] [-t|-z] [-h] [-v] <conditional> <command> DESCRIPTION when runs conditional every N seconds awaiting for "success." Success is defined in one of two ways. In timebomb mode, -t, success is defined by whether or not the conditional is still running after N seconds (as specified by the -n flag). In zero mode, -z, success is achieved when conditional exits with a return value of 0. The -n flag allows the interval to be set (in seconds) between successive attempts at running the conditional when will run until interrupted, or command completes. OPTIONS -h Prints the help message and exits successfully. -n seconds Sets the interval for running the conditional to seconds In timebomb mode, the specified time in seconds will need to pass before the conditional succeeds. -t Sets the success mode to timebomb which succeeds after conditional has been running for at least seconds -v Prints the version and exits successfully. -V Turns on verbose output. Mostly useful for debugging purposes. -z Sets the success mode to zero which succeeds after conditional returns 0 the first time. The conditional is guaranteed to be run at most 1 time every seconds NOTE Note that both conditional and command are given to "sh -c" which means that you may need to use extra quoting to get the desired effect. Note that POSIX option processing is used (i.e., option processing stops at the first non-option argument). This means that flags after conditional don't get interpreted by when itself. EXIT STATUS when makes an effort to exit with the exit status returned by the conditional in timebomb mode. In zero mode the exit status should be, well, 0. EXAMPLES TODO more examples needed Suppose you have a failing build, xmessage will alert you when it succeeds. when "make" "xmessage 'hurrah, build passed'" Or you want to say hello to john when he logs on when "w | grep john" "echo 'hello, john' | write john" Or maybe you have a daemon failing in a tight loop due to misconfiguration or lack of resources. One can run it with when and be alerted to when it becomes happy when -n 10 -t "<failing daemon>" "xmessage 'daemon running'" SEE ALSO watch(1) COPYRIGHT Copyright (C) 2013 Andrew Gwozdziewycz This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/> AUTHOR when was written by Andrew Gwozdziewycz <email@example.com> in 2013 2013 Dec 10 WHEN(1)