How to call shell script from another shell script

Question

I have two shell scripts, a.sh and b.sh.

How can I call b.sh from within the shell script a.sh?

Answer 1

First you have to include the file you call:

#!/bin/bash
. includes/included_file.sh

then you call your function like this:

#!/bin/bash
my_called_function

Answer 2

Use backticks.

$ ./script-that-consumes-argument.sh `sh script-that-produces-argument.sh`

Then fetch the output of the producer script as an argument on the consumer script.

Answer 3

The top answer suggests adding #!/bin/bash line to the first line of the sub-script being called. But even if you add the shebang, it is much faster^* to run a script in a sub-shell and capture the output:

$(source SCRIPT_NAME)

This works when you want to keep running the same interpreter (e.g. from bash to another bash script) and ensures that the shebang line of the sub-script is not executed.

For example:

#!/bin/bash
SUB_SCRIPT=$(mktemp)
echo "#!/bin/bash" > $SUB_SCRIPT
echo 'echo $1' >> $SUB_SCRIPT
chmod +x $SUB_SCRIPT
if [[ $1 == "--source" ]]; then
  for X in $(seq 100); do
    MODE=$(source $SUB_SCRIPT "source on")
  done
else
  for X in $(seq 100); do
    MODE=$($SUB_SCRIPT "source off")
  done
fi
echo $MODE
rm $SUB_SCRIPT

Output:

~ ❯❯❯ time ./test.sh
source off
./test.sh  0.15s user 0.16s system 87% cpu 0.360 total

~ ❯❯❯ time ./test.sh --source
source on
./test.sh --source  0.05s user 0.06s system 95% cpu 0.114 total

---

^* For example when virus or security tools are running on a device it might take an extra 100ms to exec a new process.

Answer 4

The answer which I was looking for:

( exec "path/to/script" )

As mentioned, exec replaces the shell without creating a new process. However, we can put it in a subshell, which is done using the parantheses.

EDIT: Actually ( "path/to/script" ) is enough.

Answer 5

There are some problems to import functions from other file.
First: You needn't to do this file executable. Better not to do so! just add

. file

to import all functions. And all of them will be as if they are defined in your file.
Second: You may be define the function with the same name. It will be overwritten. It's bad. You may declare like that

declare -f new_function_name=old_function_name 

and only after that do import. So you may call old function by new name.
Third: You may import only full list of functions defined in file. If some not needed you may unset them. But if you rewrite your functions after unset they will be lost. But if you set reference to it as described above you may restore after unset with the same name.
Finally In common procedure of import is dangerous and not so simple. Be careful! You may write script to do this more easier and safe. If you use only part of functions(not all) better split them in different files. Unfortunately this technique not made well in bash. In python for example and some other script languages it's easy and safe. Possible to make partial import only needed functions with its own names. We all want that in next bush versions will be done the same functionality. But now We must write many additional cod so as to do what you want.

Answer 6

chmod a+x /path/to/file-to-be-executed

That was the only thing I needed. Once the script to be executed is made executable like this, you (at least in my case) don't need any other extra operation like sh or ./ while you are calling the script.

Thanks to the comment of @Nathan Lilienthal