how to run one bash script from within another?

babag · 04-25-2005, 01:18 PM

i've got two small bash scripts and thought it would be nice to try to
make a third to run the first two. the first, however, takes some time
to run so the second never did run. i tried including a sleep command
but that seems awkward. would be much better to actually determine
when the first had finished rather than assigning an arbitrary time
limit, especially since the time could vary a lot depending on how
much material the first script had to deal with. how do you do this?
my script follows.

thanks,
BabaG

#!/bin/bash

exec ./30fps_to_24fps
sleep 60
exec ./renumber_30fps_to_24fps

done

ahh · 04-25-2005, 01:37 PM

Code:

#!/bin/bash

exec ./30fps_to_24fps && exec ./renumber_30fps_to_24fps

done

This will run the second script if the first script exits successfully.

babag · 04-25-2005, 01:41 PM

hey thanks!

jlliagre · 04-25-2005, 02:16 PM

The exec builtin command is useless in these scripts, here's a simpler version

Code:

#!/bin/sh
./30fps_to_24fps && ./renumber_30fps_to_24fps

R00ts · 04-25-2005, 02:38 PM

Here's a related by somewhat off-topic question. Is there another way to tell if a program exited successfully in bash? Ie, can you check for a non-zero return value? I have a somewhat complex script that executes a multitude of commands (and checks for various file/directory structures between the commands) so I can't really just put them all in a single line seperated by &&. I've been reading the Advanced BASH scripting guide but haven't been able to find that section yet.

ahh · 04-25-2005, 02:52 PM

Code:

echo $?

will provide the exit status of the last executed command.

babag · 04-27-2005, 12:19 AM

can someone post an example of how to do this without having the
various scripts on the same line and linked by &&? i'd like to have a
master script containing a bunch of different scripts. would be nice
to be able to keep it flexible, placing a script command on each line
and commenting out the lines for scripts i don't want to run and
uncommenting the lines for the scripts i do want to run. is this
practical?

also, tried ahh's example above but the second script didn't run.

jlliagre · 04-27-2005, 01:25 AM

If you just want the script to abort should one of the subscripts fails, here's one way:

Code:

#!/bin/bash

subscript1 || exit
subscript2 arg1 arg2 || exit
# subscript3 || exit # disabled
subscript4 || exit

...

ahh · 04-27-2005, 10:01 AM

Quote:

Originally posted by babag
...also, tried ahh's example above but the second script didn't run.

If your second script didn't run, it is because the last command run in your first script failed.

An example:-
If the last command in your first script was

Code:

[ -f /home/me/file.txt ] && echo "file exists"

and the file /home/me/file.txt does not exist, the test will fail and return an exit code of 1. As this is the last command run in your first script the script will return an exit code of 1, thus the second script will not run.

If the file does exist, the test will pass, and the echo command will run. If the echo command is successful it will return an exit code of 0, your first script will exit with an exit code of 0, and the second script will run.

If you are not aware, a successful command returns an exit code of 0, an unsucessful one another number. Simple commands are usually just 0 or 1, but the programmer may designate other numbers to specify why the command was unsuccessful.

If you want a script to exit with a code of 0 whatever happens, simply write

Code:

exit 0

as the last line.

Using the script from jlliagre as another example, you could write

Code:

#!/bin/bash

subscript1 || exit 1
subscript2 arg1 arg2 || exit 2
# subscript3 || exit 3# disabled
subscript4 || exit 4

exit 0

Now if you run the script from a terminal, you can type

Code:

echo $?

after it is done and it will print the exit code. From this you will know if it was successful, or if not, where it failed.

babag · 04-28-2005, 12:12 AM

hey thanks folks! very helpful. i'll be playing with these over the next few days
for sure. being that i'm ganging together multiple scripts performing many
operations, i may be gone for a while to try to figure this out. thanks again!