bash
bash --versionNotes
Useful when checking feature support such as associative arrays or newer shell options.
Bash Cheat Sheet
Comprehensive Bash commands, shell syntax, quoting, variables, redirection, pipelines, and day-to-day scripting patterns.
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Invocation and Help
Start Bash, inspect version, and open a clean shell.
bash
bash -lNotes
Loads login startup files such as /etc/profile and ~/.bash_profile depending on system configuration.
bash
bash --noprofile --norcNotes
Useful for debugging startup configuration problems.
bash
bash -lc 'echo "$SHELL" && pwd'Notes
Common in CI, Docker, and automation where you need Bash semantics for one command.
bash
bash -n script.shNotes
Good first step before running a script in production or CI.
bash
bash -x script.shNotes
Helps debug variable expansion and flow control problems.
Shell Basics
Basic commands, chaining, and status codes.
bash
echo $?Notes
A zero status means success by convention.
bash
mkdir -p tmp && cd tmp && pwdNotes
Use && for fail-fast sequences.
bash
grep -q needle file.txt || echo 'not found'Notes
Use || for error handling or defaults.
bash
{ echo start; date; echo end; }Notes
Braces keep variable changes in current shell when syntax is valid.
bash
( cd /tmp && pwd )Notes
Directory changes and variables do not leak back to parent shell.
bash
ps aux | grep nginx | grep -v grepNotes
Pipelines are foundational to shell workflows.
bash
set -o pipefailNotes
Important for reliable scripts; otherwise only final pipeline status is returned.
Redirection
Redirect stdin, stdout, stderr, and combine streams.
bash
echo 'hello' > out.txtNotes
Use >> to append instead of overwrite.
bash
echo 'hello' >> out.txtNotes
Useful for logs and generated reports.
bash
grep needle missing.txt 2> errors.logNotes
File descriptor 2 is stderr.
bash
command > all.log 2>&1Notes
Very common for logs and debugging shell jobs.
bash
command > /dev/null 2>&1Notes
Useful in scripts when output is expected but unneeded.
bash
cat <<'EOF'
line 1
$HOME is not expanded here
EOFNotes
Quoted delimiter disables parameter expansion.
bash
grep -o '[0-9]\+' <<< 'order-123'Notes
Useful for compact one-liners and tests.
bash
while IFS= read -r line; do echo "$line"; done < input.txtNotes
The IFS= and -r pattern is the standard safe read loop.
More in Bash
Bash Scripting Patterns and Practical Recipes
Production-minded Bash script patterns for files, arguments, parsing, temp files, logging, retries, and common automation tasks.
Bash Builtins, Job Control, and Shell Behavior
Core Bash builtins, shell options, history, aliases, job control, traps, and interactive-shell behavior.
Bash Arrays, Strings, and Text Handling
Indexed and associative arrays, string handling, read/mapfile, and common Bash text-processing patterns.
Bash Conditionals, Loops, and Functions
Bash if/elif/case logic, test expressions, loops, functions, return codes, and robust control-flow patterns.
Bash Variables, Quoting, and Expansion
Bash variables, parameter expansion, quoting rules, command substitution, arithmetic, and shell expansion patterns.
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