Bash Cron Script¶

Introduction¶

This Bash guide covers bash cron script with scripts that can be tested on a normal Linux host. The examples use safe defaults, quoted variables, and explicit error handling.

Basic Syntax¶

name="server1"
printf "host=%s\n" "$name"

The shell expands variables, runs commands, and uses exit codes to decide whether a step succeeded.

Practical Examples¶

#!/usr/bin/env bash
set -euo pipefail

path="/var/log"
if [[ -d "$path" ]]; then
  du -sh "$path"
fi

Real-World Script Example¶

#!/usr/bin/env bash
set -euo pipefail

target="${1:-/tmp}"
if [[ ! -e "$target" ]]; then
  echo "target does not exist: $target" >&2
  exit 1
fi

printf "checking %s\n" "$target"
ls -ld "$target"

Error Handling¶

if ! systemctl is-active --quiet sshd; then
  echo "sshd is not running" >&2
  exit 1
fi

Use clear messages and non-zero exits so cron, CI jobs, and monitoring tools can detect failure.

Testing the Script¶

bash -n script.sh
chmod +x script.sh
./script.sh /var/log
echo $?

Expected output:

checking /var/log
drwxr-xr-x. 12 root root 4096 May 30 09:55 /var/log
0

Common Mistakes¶

• Making several changes at once, which hides the real cause.
• Skipping logs or verification commands after a change.
• Assuming the problem is fixed because one command returned successfully.

Best Practices¶

• Use strict mode for administrative scripts.
• Print useful errors to standard error.
• Keep scripts idempotent when they change system state.
• Validate inputs before running privileged commands.

Related Guides¶

• Bash Error Handling
• Bash Debugging
• Bash Scripting Best Practices
• Bash Script Security

Summary¶

Good Bash scripts are predictable: validate input, quote variables, handle errors, and test realistic failure cases before using them in automation.