I've a bash-script that starts some service in background. After this service successfully starts it prints "Server is active" to the stdout. I need to wait until this string appears and then continue executing my script. How can I achieve this?
4 Answers
I would do in this way.
./server > /tmp/server-log.txt & sleep 1 while ! grep -m1 'Server is active' < /tmp/server-log.txt; do sleep 1 done echo Continue Here -m1 tells grep(1) to quit at the first match.
I veryfied my answer with my toy "service" below:
#! /bin/bash trap "echo 'YOU killed me with SIGPIPE!' 1>&2 " SIGPIPE rm -f /tmp/server-output.txt for (( i=0; i<5; ++i )); do echo "i==$i" sleep 1; done echo "Server is active" for (( ; i<10; ++i )); do echo "i==$i" sleep 1; done echo "Server is shutting down..." > /tmp/server-output.txt If you replace echo Continue with echo Continue; sleep 1; ls /tmp/server-msg.txt, you will see ls: cannot access /tmp/server-output.txt: No such file or directory which proves the "Continue" action was triggered right after the output of Server is active.
Comments
Use grep -q. The -q option makes grep quiet, and it will exit immediately when the text appears.
The command below starts ./some-service in the background, and blocks until "Server is active" appears on stdout.
(./some-service &) | grep -q "Server is active" answered Jul 26, 2019 at 8:14
Lars Christian Jensen
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1 Comment
Anu Shibin Joseph Raj
This is awesome! I did something like this:
/opt/mssql/bin/sqlservr > /root/sqlservr.out & and then tail -f /root/sqlservr.out | grep -q "SQL Server is now ready"For me to read service's status as to service app:
$ /sbin/service network status network.service - Network Connectivity Loaded: loaded (/lib/systemd/system/network.service; enabled) Active: active (exited) since Ср 2014-01-29 22:00:06 MSK; 1 day 15h ago Process: 15491 ExecStart=/etc/rc.d/init.d/network start (code=exited, status=0/SUCCESS) $ /sbin/service httpd status httpd.service - SYSV: Apache is a World Wide Web server. It is used to serve HTML files and CGI. Loaded: loaded (/etc/rc.d/init.d/httpd) Active: activating (start) since Пт 2014-01-31 13:59:06 MSK; 930ms ago and it can be done with the code:
function is_in_activation { activation=$(/sbin/service "$1" status | grep "Active: activation" ) if [ -z "$activation" ]; then true; else false; fi return $?; } while is_in_activation network ; do true; done 
Comments
Are you asking redirect stderr to stdout?
./yourscript.sh 2>&1 |grep "Server is active" && echo "continue executing my script" 
systemdor plain old SysV init....stdouthere.