bash function to check for something every 5 seconds

function checkfor () { while :; do $*; sleep 5; done; }
checkfor: have the shell check anything you're waiting for. 'while : ; do' is an infinite loop '$*' executes the command passed in 'sleep 5' - change for your tastes, sleep for 5 seconds bash, ksh, likely sh, maybe zsh Ctrl-c to break the loop
Sample Output
# waiting for a DNS change to showup
checkfor dig | egrep -A1 ';; ANSWER'
;; ANSWER SECTION:                434     IN      A
# OR
# Waiting for a results file
checkfor ls -la file_i_am_waiting_for
ls: file_i_am_waiting_for: No such file or directory
ls: file_i_am_waiting_for: No such file or directory
-rw-r--r-- 1 smith software 0 Sep  3 12:18 file_i_am_waiting_for
checkfor ls -la file_i_am_waiting_for  2> /dev/null # if you don't want errors
-rw-r--r-- 1 smith software 0 Sep  3 12:33 /tmp/file_i_am_waiting_for

By: relay
2009-09-03 19:35:42

1 Alternatives + Submit Alt

What Others Think

Note that the function and the "watch -n" commands behave differently with regards to quoting, although syntactically look the same.
EFraim · 637 weeks and 4 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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