LinuxQuestions.org - Trouble With FOR Loop In Simple Bash Script

- Linux - Newbie (https://www.linuxquestions.org/questions/linux-newbie-8/)

- - Trouble With FOR Loop In Simple Bash Script (https://www.linuxquestions.org/questions/linux-newbie-8/trouble-with-for-loop-in-simple-bash-script-627247/)

Trouble With FOR Loop In Simple Bash Script

I thought I copied the following script correctly, but it doesn't seem to work. In particular, although I can type ps auxww | etc at the command line and get a PID, the for loop in the script doesn't run:

Code:

#! /bin/bash

#

echo -n "Stopping rsyncd:  ";

for pid in $( ps auxww | grep "rsync" | grep -v grep | grep -v pico | cut -c10-14 );

do

kill -9 $pid;

rm -f /var/lock/rsyncd.lock;

echo "[ OK ]";

exit;

done;

echo "[ FAILURE ]";

1. Why doesn't the for loop run?
2. Do I need all those semicolons?
3. After you get this working, do you see any way to simplify it?
4. Is there a tutorial on shell scripts which covers the concepts I've missed?

Quote:

Originally Posted by sudleyplace (Post 3085134)

Why doesn't the for loop run?

Because you exit prematurely? Debugging helps show that: try running the script as 'sh -vx scriptname'.

Quote:

Originally Posted by sudleyplace (Post 3085134)

Do I need all those semicolons?

Not unless you want to string commands together: "for item in something; do action; action && { echo OK; exit 0; }; done; exit 0"

Quote:

Originally Posted by sudleyplace (Post 3085134)

After you get this working, do you see any way to simplify it?

It's a common mistake to use 'ps' to grep for PIDs. Instead you could use 'pgrep'.
Even better, you can combine pgrep and kill and use 'pkill' instead: pkill -9 -f 'rsync'.

Quote:

Originally Posted by sudleyplace (Post 3085134)

Is there a tutorial on shell scripts which covers the concepts I've missed?

http://www.tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html
http://www.tldp.org/LDP/Bash-Beginne...tml/index.html
http://www.tldp.org/LDP/abs/html/

See killall, which will do what you are trying to script.

Quote:

Originally Posted by unSpawn (Post 3085180)

Because you exit prematurely? Debugging helps show that: try running the script as 'sh -vx scriptname'.

Thanks -- knowing the debug commands helps a lot.

Quote:

Originally Posted by unSpawn (Post 3085180)

Not unless you want to string commands together: "for item in something; do action; action && { echo OK; exit 0; }; done; exit 0"

OK, now I understand.

Quote:

Originally Posted by unSpawn (Post 3085180)

It's a common mistake to use 'ps' to grep for PIDs. Instead you could use 'pgrep'.
Even better, you can combine pgrep and kill and use 'pkill' instead: pkill -9 -f 'rsync'.

I don't seem to have a pgrep or pkill on my system (WestHost.com), however ps seems to work in this context. Am I missing something (besides pgrep/pkill)?

I did figure out why the for loop didn't execute correctly. I did a copy and paste to get the original script, however that script contained a spurious character (\224) in it which does not display. When I ran the script through the shell debugger, I saw the extraneous char. Removing it allowed the script to run.

Quote:

Originally Posted by unSpawn (Post 3085180)

http://www.tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html
http://www.tldp.org/LDP/Bash-Beginne...tml/index.html
http://www.tldp.org/LDP/abs/html/

All good references. Many thanks!

Quote:

Originally Posted by sudleyplace (Post 3085342)

I don't seem to have a pgrep or pkill on my system (WestHost.com)

If you run a VPS there maybe you could install the package. It's standard, not exotic. Good you found out the char thing.

Another very good Linux tutorial: http://rute.2038bug.com/index.html.gz

Quote:

Originally Posted by unSpawn (Post 3085594)

If you run a VPS there maybe you could install the package. It's standard, not exotic. Good you found out the char thing.

I found another tool killproc (similar to pkill) and part of the source function library /etc/init.d/functions which makes it easy to remove a program.

Quote:

Originally Posted by chrism01 (Post 3085689)

Another very good Linux tutorial: http://rute.2038bug.com/index.html.gz

Thanks for the reference.