Testing if a Daemon is alive or not with Shell -

i have log_sender.pl perl script when executed runs daemon. want make test, using shell:

 #!/bin/bash                                                                                                                                 function log_sender()  {      perl -i $home/script/log_sender.pl  }   (    [[ "${bash_source[0]}" == "${0}" ]] || exit 0    function check_log_sender()       {           if [ "ps -aef | grep -v grep log_sender.pl" ];               echo "passed"               else               echo failed           fi      }        log_sender      check_log_sender   ) 

unfortunately when run terminal becomes:

 -bash-4.1$ sh log_sender.sh   ...     ... 

what doing wrong?

> if [ "ps -aef | grep -v grep log_sender.pl" ]; 

this not want. try this:

if ps -aef | grep -q 'log_sender\.pl';     ... 

in shell script, if construct takes argument command exit status examines. in code, command [ (also known test) , run on literal string "ps -aef | grep -v grep log_sender.pl" true.

you intended check whether ps -aef outputs line contains log_sender.pl not contain grep; ps -aef | grep -v grep | grep 'log_sender\.pl' can avoid grep -v specifying regular expression not match itself.

the -q option grep suppresses output; exit code indicates whether or not input matched regular expression.

the perl invocation not correct; -i option requires argument, saying perl , perl interpreter waiting type in perl script execute. apparently script log_sender.pl should drop -i (or add argument it, if need add perl library paths in order script work).

finally, if write bash script, should execute bash.

chmod +x log_sender.sh ./log_sender.sh 

or alternatively

bash ./log_sender.sh 

the bash_source construct use bashism, script not work correctly under sh.

finally, parentheses around main logic redundant. cause script run these commands in separate subshell no apparent benefit.