[bash] How to call one shell script from another shell script?

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

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

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.

There are a couple of different ways you can do this:

1. Make the other script executable, add the #!/bin/bash line at the top, and the path where the file is to the $PATH environment variable. Then you can call it as a normal command;

2. Or call it with the source command (alias is .) like this: source /path/to/script;

3. Or use the bash command to execute it: /bin/bash /path/to/script;

The first and third methods execute the script as another process, so variables and functions in the other script will not be accessible.
The second method executes the script in the first script's process, and pulls in variables and functions from the other script so they are usable from the calling script.

In the second method, if you are using exit in second script, it will exit the first script as well. Which will not happen in first and third methods.

Assume the new file is "/home/satya/app/app_specific_env" and the file contents are as follows

#!bin/bash

export FAV_NUMBER="2211"

Append this file reference to ~/.bashrc file

source /home/satya/app/app_specific_env

When ever you restart the machine or relogin, try echo $FAV_NUMBER in the terminal. It will output the value.

Just in case if you want to see the effect right away, source ~/.bashrc in the command line.

There are a couple of ways you can do this. Terminal to execute the script:

#!/bin/bash
SCRIPT_PATH="/path/to/script.sh"

# Here you execute your script
"$SCRIPT_PATH"

# or
. "$SCRIPT_PATH"

# or
source "$SCRIPT_PATH"

# or
bash "$SCRIPT_PATH"

# or
eval '"$SCRIPT_PATH"'

# or
OUTPUT=$("$SCRIPT_PATH")
echo $OUTPUT

# or
OUTPUT=`"$SCRIPT_PATH"`
echo $OUTPUT

# or
("$SCRIPT_PATH")

# or
(exec "$SCRIPT_PATH")

All this is correct for the path with spaces!!!

If you have another file in same directory, you can either do:

bash another_script.sh

or

source another_script.sh

or

. another_script.sh

When you use bash instead of source, the script cannot alter environment of the parent script. The . command is POSIX standard while source command is a more readable bash synonym for . (I prefer source over .). If your script resides elsewhere just provide path to that script. Both relative as well as full path should work.

 #!/bin/bash

 # Here you define the absolute path of your script

 scriptPath="/home/user/pathScript/"

 # Name of your script

 scriptName="myscript.sh"

 # Here you execute your script

 $scriptPath/$scriptName

 # Result of script execution

 result=$?

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

This was what worked for me, this is the content of the main sh script that executes the other one.

#!/bin/bash 
source /path/to/other.sh

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.

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

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.

You can use /bin/sh to call or execute another script (via your actual script):

 # cat showdate.sh
 #!/bin/bash
 echo "Date is: `date`"

 # cat mainscript.sh
 #!/bin/bash
 echo "You are login as: `whoami`"
 echo "`/bin/sh ./showdate.sh`" # exact path for the script file

The output would be:

 # ./mainscript.sh
 You are login as: root
 Date is: Thu Oct 17 02:56:36 EDT 2013

Simple source will help you. For Ex.

#!/bin/bash
echo "My shell_1"
source my_script1.sh
echo "Back in shell_1"

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.

Check this out.

#!/bin/bash
echo "This script is about to run another script."
sh ./script.sh
echo "This script has just run another script."

pathToShell="/home/praveen/"   
chmod a+x $pathToShell"myShell.sh"
sh $pathToShell"myShell.sh"

Just add in a line whatever you would have typed in a terminal to execute the script!
e.g.:

#!bin/bash
./myscript.sh &

if the script to be executed is not in same directory, just use the complete path of the script.
e.g.:`/home/user/script-directory/./myscript.sh &

Depends on. Briefly... If you want load variables on current console and execute you may use source myshellfile.sh on your code. Example:

!#/bin/bash
set -x
echo "This is an example of run another INTO this session."
source my_lib_of_variables_and_functions.sh
echo "The function internal_function() is defined into my lib."
returned_value=internal_function()
echo $this_is_an_internal_variable

set +x

If you just want to execute a file and the only thing intersting for you is the result, you can do:

!#/bin/bash
set -x
./executing_only.sh
sh i_can_execute_this_way_too.sh
bash or_this_way.sh
set +x

I hope helps you. Thanks.