Multiple Ways to Execute Shell Scripts and Manage Permissions

Shell scripts can be run using various techniques, each requiring appropriate execution permissions.

1. Interpreter execution – run the script by explicitly invoking the interpreter, e.g., /bin/bash script.sh .

2. Relative‑path execution – after granting execute permission, run the script from its directory:

chmod +x first.sh

./first.sh

Output: Hello World!

3. Absolute‑path execution – similarly grant permission and call the script with its full path:

chmod o+x first.sh

pwd (shows /root)

/root/first.sh

Output: Hello World!

4. Dot‑source execution – source the script in the current shell:

. first.sh

Output: Hello World!

5. Using the source builtin – equivalent to dot‑source:

source first.sh

Output: Hello World!

In production environments, it is generally recommended to execute scripts without adding extra permissions.

Extended content – interpreter list – the file /etc/shells lists available shells such as /bin/sh, /bin/bash, /sbin/nologin, /usr/bin/sh, /usr/bin/bash, /bin/tcsh, /bin/csh.

Linux permission basics – the ll (or ls -l ) command shows file mode bits; for example, -rw-r--r-- means read/write for owner, read for group and others. Permission bits are r (read), w (write), x (execute).

Changing permissions with chmod – syntax: chmod [u,g,o] [+-=] [rwx] file . Examples:

chmod u+x first.sh → -rwxr--r--

chmod u-x first.sh → -rw-r--r--

chmod +x first.sh → -rwxr-xr-x