cat Cheatsheet
Quick reference for viewing, combining, and redirecting file content with cat in Linux
The cat command prints and concatenates file content in Linux. This cheatsheet covers common viewing patterns, line-number options, safe redirection, and practical command combinations.
Basic Syntax
Core cat command forms.
| Command | Description |
|---|---|
cat FILE | Print a file to standard output |
cat FILE1 FILE2 | Print multiple files in sequence |
cat | Read from standard input until EOF |
cat -n FILE | Show all lines with line numbers |
cat -b FILE | Number only non-empty lines |
View File Content
Common read-only usage patterns.
| Command | Description |
|---|---|
cat /etc/os-release | Print distro information file |
cat file.txt | Show full file content |
cat file1.txt file2.txt | Show both files in one stream |
cat -A file.txt | Show tabs/end-of-line/non-printing chars |
cat -s file.txt | Squeeze repeated blank lines |
Line Numbering and Visibility
Inspect structure and hidden characters.
| Command | Description |
|---|---|
cat -n file.txt | Number all lines |
cat -b file.txt | Number only non-blank lines |
cat -E file.txt | Show $ at end of each line |
cat -T file.txt | Show tab characters as ^I |
cat -v file.txt | Show non-printing characters |
Combine Files
Create merged outputs from multiple files.
| Command | Description |
|---|---|
cat part1 part2 > merged.txt | Merge files into a new file |
cat header.txt body.txt footer.txt > report.txt | Build one file from sections |
cat a.txt b.txt c.txt > combined.txt | Join several text files |
cat file.txt >> archive.txt | Append one file to another |
cat *.log > all-logs.txt | Merge matching files (shell glob) |
Create and Append Text
Use cat with redirection and here-docs.
| Command | Description |
|---|---|
cat > notes.txt | Create/overwrite a file from terminal input |
cat >> notes.txt | Append terminal input to a file |
cat <<'EOF' > config.conf | Write multiline text safely with a here-doc |
cat <<'EOF' >> config.conf | Append multiline text using a here-doc |
cat > script.sh <<'EOF' | Create a script file from inline content |
Pipelines and Common Combos
Practical command combinations with other tools.
| Command | Description |
|---|---|
cat access.log | grep 500 | Filter matching lines |
cat file.txt | wc -l | Count lines |
cat file.txt | head -n 20 | First 20 lines |
cat file.txt | tail -n 20 | Last 20 lines |
cat file.txt | tee copy.txt >/dev/null | Copy stream to a file |
Troubleshooting
Quick checks for common cat usage issues.
| Issue | Check |
|---|---|
Permission denied | Check ownership and file mode with ls -l; run with correct user or sudo if required |
| Output is too long | Pipe to less (cat file | less) or use head/tail |
| Unexpected binary output | Verify file type with file filename before printing |
| File was overwritten accidentally | Use >> to append, not >; enable shell noclobber if needed |
| Hidden characters break scripts | Inspect with cat -A or cat -vET |
Related Guides
Use these guides for full file-view and text-processing workflows.
| Guide | Description |
|---|---|
| How to Use the cat Command in Linux | Full cat command guide |
| head Command in Linux | Show the first lines of files |
| tail Command in Linux | Follow and inspect recent lines |
| tee Command in Linux | Write output to file and terminal |
| wc Command in Linux | Count lines, words, and bytes |
| Create a File in Linux | File creation methods |
| Bash Append to File | Safe append patterns |