Bash Options

Shell Options Summary

• Purpose: Options modify the execution behavior of a shell or script.
• Enable Options: Use the (minus) sign.
  • Long form: set -o <option-name> (e.g., set -o verbose)
  • Short form: set -<abbrev> (e.g., set -v)
• Disable Options: Use the + (plus) sign.
  • Long form: set +o <option-name> (e.g., set +o verbose)
  • Short form: set +<abbrev> (e.g., set +v)

---

Flag Behavior Table

Option Name	Short Flag	Enable Command	Disable Command	Behavior
errexit	e	set -e	set +e	-e: Script aborts immediately if a command fails.
+e: Script ignores failures and continues (Default).
verbose	v	set -v	set +v	Prints shell input lines exactly as they are read by the interpreter.

---

Example 1: set -e (Exit on Error)

Because -e is active, the script encounters the missing file, throws an error, and terminates before reaching the echo command.

exit_on_error.sh

#!/bin/bash
set -e

echo "Check non-existing file"
cat non-existing-file.txt
echo "moving on" # This line will NEVER execute.

Output:

$ ./exit_on_error.sh Check non-existing file cat: non-existing-file.txt: No such file or directory

Example 2: set +e (Skip Error / Default)

Because +e is active (or implicitly default), the script logs the cat error but continues executing the remaining lines.

skip_error.sh

#!/bin/bash
# default value is +e
set +e

echo "Check non-existing file"
cat non-existing-file.txt
echo "moving on" # This line executes normally.

Output:

$ ./skip_error.sh Check non-existing file cat: non-existing-file.txt: No such file or directory moving on