How to Run .sh File in Linux: bash, chmod, and shebang

Q: Can I run a script without execute permission?

Yes - `bash script.sh` or `sh script.sh`. The team that uses this avoids chmod.

Q: What's a shebang?

The first line of a script starting with `#!` that tells the kernel which interpreter to use. The team that uses shebangs has portable scripts.

Q: How do I run a script in the background?

`nohup ./script.sh &` or with systemd: create a service unit. The team that has systemd manages scripts as services.

How to run .sh file in Linux: bash script.sh (no execute permission needed) or chmod +x script.sh && ./script.sh (uses the shebang line). The shebang #!/bin/bash at the top tells the kernel which interpreter to use. The team that uses chmod +x + ./script.sh has the standard execution pattern.

Method 1: bash script.sh
Method 2: chmod + execute
The shebang line
Why ./script.sh not script.sh
PATH for executables anywhere
Debugging with bash -x
Common pitfalls
FAQ

Method 1: bash script.sh

bash script.sh

No execute permission needed. The team that uses this for one-off scripts has the simplest method.

Method 2: chmod + execute

chmod +x script.sh
./script.sh

The team that uses chmod +x then ./script.sh has the standard execution. Requires the shebang line at the top of the script.

The shebang line

First line of script.sh:

#!/bin/bash

Other common shebangs:

#!/bin/sh - POSIX shell (most portable).
#!/usr/bin/env bash - finds bash in PATH (more portable).
#!/usr/bin/env python3 - for Python scripts.
#!/usr/bin/env node - for Node scripts.

The team that uses #!/usr/bin/env has portable scripts (no hardcoded path).

Why ./script.sh not script.sh

Linux doesn’t run scripts in the current directory by default (unlike Windows). The ./ prefix is needed. The team that types script.sh and gets ‘command not found’ needs the ./.

PATH for executables anywhere

For scripts to be runnable from anywhere:

mkdir -p ~/.local/bin
mv script.sh ~/.local/bin/mycommand
chmod +x ~/.local/bin/mycommand

Add ~/.local/bin to PATH (often default). The team that uses ~/.local/bin has user-installed commands runnable from anywhere.

Debugging with bash -x

bash -x script.sh

Prints each command before execution. The team that uses bash -x has full debug output for failing scripts.

Common pitfalls

Wrong shebang: #!/bin/bash but script uses sh-only syntax. The team that matches shebang to script has correct behavior.
CRLF line endings (from Windows): bash chokes. dos2unix script.sh.
No execute permission: chmod +x first.
Wrong working directory: use absolute paths or cd in script.

FAQ

Why use ./script.sh?

Linux doesn’t include the current directory in PATH (security). The team that uses ./ has explicit intent.

Can I run a script without execute permission?

Yes - bash script.sh or sh script.sh. The team that uses this avoids chmod.

What’s a shebang?

The first line of a script starting with #! that tells the kernel which interpreter to use. The team that uses shebangs has portable scripts.

How do I run a script in the background?

nohup ./script.sh & or with systemd: create a service unit. The team that has systemd manages scripts as services.

Can I make a script run at boot?

Yes - via systemd service, cron @reboot, or /etc/rc.local. The team that uses systemd has proper service management.

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