Disk Space Warning Script
Copy a disk space warning bash script using df, thresholds, cron, and email alerts. Monitor Linux se...
Full guide →$bash-snippets
Bash Script Library
68 copy-paste bash scripts with plain-English explanations. ShellCheck-clean.
68scripts
14free tools
0logins required
Beginner Scripts (30)
Automated File Backup
A deleted file on Linux has no undo. This bash backup script timestamps every cp -r run with a date...
Full guide →Quick System Info Report
Guessing server state mid-outage costs time. One bash script reports hostname, uptime, CPU load, RAM...
Full guide →Search Files for Text with grep
Opening files one by one to find a string wastes time. grep -rn searches every file under a director...
Full guide →Check If Website Is Up
Learning a site is down from a user complaint means the outage already cost you. A bash curl check t...
Full guide →Bash If/Else Examples
The wrong comparison operator makes a bash if statement fail silently on unexpected input. if/else,...
Full guide →Create a Dated Folder
Backup folders without dates overwrite old runs and sort unpredictably. date +%Y-%m-%d names each fo...
Full guide →Find Large Files in Linux
Disk at 100% and the server stopped. Find the biggest files and directories fast with du and find, s...
Full guide →Kill Process on Port
EADDRINUSE means something already holds your port. Find the process with lsof or ss and kill it saf...
Full guide →List All Open Ports on Linux
A bash script that maps every port your server is listening on, along with the process name holding...
Full guide →Docker Cleanup Bash Script — Reclaim Disk Space from Docker Garbage
A bash script that removes stopped containers, unused images, dangling volumes, and build cache from...
Full guide →Bash For Loop Examples
A for loop over ls output splits filenames with spaces and skips files silently. Loop over a glob, r...
Full guide →Find and Replace in Files with sed (Without Corrupting Half Your Tree)
Find and replace text in files with sed: in-place edits, GNU vs macOS -i, word boundaries, capture g...
Full guide →Find Your IP Address on Linux: Local, Public, Gateway, DNS, and MAC
A firewall rule built on the wrong IP locks you out. Find your local, public, gateway, DNS, and MAC...
Full guide →Bash Environment Variables: export, unset, Subshells, and Why Cron Can't See Yours
A variable you never exported is invisible to child processes, so the deploy reads an empty token an...
Full guide →Port Is Listening but Connection Refused: Check the Bind Address — Bash Script
ss shows the port listening, yet other machines get Connection refused. The service is bound to 127....
Full guide →journalctl Disk Usage: Check and Limit the systemd Journal Size — Bash Script
The systemd journal keeps logs until its own cap, up to 4G by default. Check it with journalctl --di...
Full guide →/bin/bash^M: bad interpreter — Fix CRLF Line Endings in Bash Scripts
/bin/bash^M: bad interpreter means the script has Windows CRLF line endings. Find them with file or...
Full guide →Fix "bash: command not found": PATH, Typos, hash -r, CRLF and Cron
Fix bash: command not found: check PATH, typos, a stale hash table, CRLF line endings and sudo's PAT...
Full guide →Fix "unary operator expected" in Bash: Empty Variables in [ ]
Fix bash unary operator expected errors: an empty variable inside [ ] vanishes. Quote it, switch to...
Full guide →Fix "Permission denied" in Bash: chmod, noexec, Directories and Exit 126
Fix Permission denied when running a bash script: chmod +x, directory search bits, noexec mounts and...
Full guide →ss Command Examples: -tulpn, Port Filters and What Each Column Means
Copy-paste ss command examples: -tulpn, port and state filters, -s, and the netstat equivalents, wit...
Full guide →Remove All Docker Containers Safely: Stopped, Running, Filtered
Remove all Docker containers in two commands, plus the filters, the empty-list error, what survives...
Full guide →AWK Cheat Sheet: Print Columns, Filter Rows, Sum and Count (Run-Verified)
AWK cheat sheet with run-verified one-liners: print a column, filter rows, sum a field, count by key...
Full guide →Bash While Loop Examples: read -r, the Pipe Subshell Trap, until and Timeouts
Bash while loop examples that survive production: read -r line loops, the pipe-subshell variable tra...
Full guide →Bash Case Statement Examples: Patterns, Order, ;;& and ;& Fallthrough
Bash case statement examples with real output: glob patterns, | alternatives, why pattern order matt...
Full guide →scp Command Examples for Scripts: Push, Pull, Spaces, -O and Exit Codes
scp command examples run for real: push, pull, -r, -p, remote paths with spaces, OpenSSH 9+ SFTP mod...
Full guide →Cron Job Not Running? 7 Checks That Find the Cause
Cron job not running? Seven checks in order: the daemon, the schedule, permissions, cron's PATH, une...
Full guide →Ubuntu 26.04 Rust Coreutils: Check Which One You Run and Switch Back to GNU
Ubuntu 26.04 runs most coreutils from Rust (uutils) but keeps cp, mv and rm GNU. See which one each...
Full guide →Fix systemd "status=203/EXEC": Five Causes and How to Tell Them Apart
status=203/EXEC means systemd could not start your program at all. The journal line names which of f...
Full guide →Intermediate Scripts (38)
Delete Old Log Files
Unmanaged logs fill /var/log until writes fail and services crash. find -mtime deletes .log files ol...
Full guide →Bash Error Handling with set -euo pipefail
Bash keeps going after a failed command, so a broken cd followed by rm -rf hits the wrong directory....
Full guide →Kill a Process with pkill and pgrep
ps, grep, copy the PID, kill: four steps every time. pkill stops a process by name in one command, a...
Full guide →File Permissions Security Audit
A world-writable file on a web server lets a compromised script overwrite your app. Audit permission...
Full guide →Monitor CPU and RAM Usage
A runaway process at 100% CPU goes unnoticed until the server stops responding. Measure CPU and RAM...
Full guide →Send Email Alerts from Bash
A monitoring script with no email alert fails silently until users notice. A reusable bash alert fun...
Full guide →MySQL Database Backup Script
A mistaken DROP TABLE has no undo. Back up MySQL nightly with mysqldump and gzip, rotate dumps older...
Full guide →SSH Key Setup Script
Password SSH on an internet-facing server invites brute-force attempts. A bash script runs ssh-keyge...
Full guide →Find Duplicate Files in Linux
Duplicate files pile up in archives and downloads and waste gigabytes. md5sum hashes every file and...
Full guide →Restart a Service If It Stopped
A crashed nginx or PostgreSQL stays down for hours with no watchdog. A cron script uses systemctl is...
Full guide →Rsync Remote Backup
A local-only backup dies with the machine. Push an incremental, resumable copy to a remote server wi...
Full guide →Check SSL Certificate Expiry with Bash
A bash script that connects to any domain over TLS, reads the certificate, and tells you how many da...
Full guide →Read a File Line by Line in Bash
A while-read loop silently skips the last line of a file with no final newline. Read files line by l...
Full guide →Bash Functions and Arguments
A function reused 'target' without local, overwrote the caller's variable, and cleanup deleted the w...
Full guide →Bash Functions: Return Values, Local Scope, and Reusable Logic
return in a bash function sets an exit code, not a string. Return data with echo and command substit...
Full guide →Bash Arrays: Indexed, Associative, Append, and Safe Iteration
A list stored as a space-separated string splits once an item has a space. Bash arrays fix it: index...
Full guide →Bash Argument Parsing: Positional Args, getopts, and Long Flags
A script that reads $1 as a value takes --env as that value and deploys nowhere. Parse arguments wit...
Full guide →Bash String Manipulation: Substrings, Replace, and Parameter Expansion
cut -d/ -f3 returns the wrong slice once a URL gains https. Bash parameter expansion: substrings, pr...
Full guide →Prevent Overlapping Cron Jobs with flock
A long cron job overlaps its next run and stacks copies until the box falls over. flock locks it to...
Full guide →Stop a Hung Command with timeout
A hung cron job never exits, never frees its lock, and quietly stops the job running. Bound a comman...
Full guide →Retry a Command with Exponential Backoff in Bash
A deploy that dies on the first transient error costs a night of manual re-runs. Retry with exponent...
Full guide →Make API Requests in Bash with curl (That Actually Fail When the API Does)
Plain curl exits 0 on an HTTP 500 and poisons everything downstream. A bash curl wrapper that checks...
Full guide →Parse JSON in Bash with jq (Stop Using grep and cut on API Responses)
Read fields from a JSON API response with jq, and the three things (-r, // defaults, -e) that keep t...
Full guide →Send Slack Alerts from Bash with Incoming Webhooks (So Cron Jobs Stop Failing Silently)
Post failure alerts to Slack from bash with curl, a jq-built payload and an ERR trap, so a broken ba...
Full guide →Bash trap: Clean Up Temp Files on Exit (Even When the Script Dies)
A script that dies mid-run leaves temp files and half-written output behind. trap on EXIT with mktem...
Full guide →Run Commands on a Remote Server over SSH from Bash (One Host or Twenty)
An ssh loop that ignores exit codes reports done while three hosts never changed. Run one command or...
Full guide →Audit Listening Ports and Alert on New Ones — Bash Script
A bash script that snapshots every listening TCP and UDP socket as CSV, diffs it against the previou...
Full guide →Service Watchdog: Check a systemd Unit and Restart It Once — Bash Script
A cron bash watchdog for systemd units: restarts a stopped service, probes a hung one, bounds start-...
Full guide →Log Retention Cleanup: Keep the Newest N, Delete Older Than D Days — Bash Script
A logrotate alternative for directories it does not own: keep the newest N dated folders, delete the...
Full guide →bashlib Starter: 10 Bash Functions to Source Into Every Script
Every script re-invents strict mode, ERR traps, temp cleanup and a lock, or forgets one. Source ten...
Full guide →No Space Left on Device but df Shows Free Space: Out of Inodes — Bash Script
Writes fail with No space left on device while df -h shows free space: the filesystem is out of inod...
Full guide →Argument List Too Long: Delete or Move Thousands of Files in Bash
rm *.log fails with Argument list too long and deletes nothing: the glob outgrew ARG_MAX. Use find -...
Full guide →lsof Command Examples: Ports, Open Files and Deleted Files Eating Your Disk
lsof examples for three real jobs: which process holds a port, who has a file or directory open, and...
Full guide →Bash Heredoc: <<EOF, Quoted 'EOF', <<- Indentation and Here-Strings
Bash heredoc explained with real runs: quoted vs unquoted EOF and what expands, <<- and the tabs-onl...
Full guide →Fix sudo-rs "wildcards are not allowed in command arguments" on Ubuntu 26.04
Ubuntu 26.04's sudo-rs drops sudoers rules with wildcards in arguments, then denies the command. See...
Full guide →Fix sudo-rs "I'm sorry user. I'm afraid I can't do that" on Ubuntu 26.04
sudo-rs on Ubuntu 26.04 says I'm afraid I can't do that for a missing rule, a dropped rule or one wr...
Full guide →Rust Coreutils vs GNU: The Differences That Break Bash Scripts on Ubuntu 26.04
Ubuntu 26.04's Rust coreutils change timeout's exit code, error text and edge cases scripts rely on....
Full guide →Fix systemd "Start request repeated too quickly" (start-limit-hit)
Start request repeated too quickly means systemd stopped restarting a crashing service. Find the err...
Full guide →Free Interactive Tools
Need a cron expression? chmod calculator?
14 browser-based bash tools — no install required
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The Production Bash Toolkit
An operational script system + a 30-function shared library + a 52-page field guide. The production layer the free snippets don't cover.
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