bashANYcatgreppipeline
bash
cat app.log | grep ERRORUse a pipeline to send command output into another command for filtering or transformation.
Linux Text Processing Cheat Sheet
Core Linux text processing commands and shell patterns for searching, filtering, editing, formatting, and analyzing text files and streams.
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Overview and Core Patterns
Common text processing building blocks and pipeline patterns.
bashANYgrepsearchfile
bash
grep ERROR app.logThis is more efficient than using `cat file | grep ...` for most cases.
bashANYstdinawkpipeline
bash
journalctl -u nginx | awk '{print $1, $2, $3}'Most Linux text tools are designed for stream processing and work especially well in pipelines.
bashANYteepipelinedebugging
bash
grep ERROR app.log | tee errors.txt | wc -l`tee` is useful when debugging pipelines or capturing intermediate results.
bashANYpipelineformattingshell
bash
ps aux
| grep python
| grep -v grep
| awk '{print $2, $11}'Long shell pipelines become much easier to read and maintain when formatted over multiple lines.
Line Selection and Context
Pick lines, ranges, and context quickly.
bashANYheadpreview
bash
head -n 20 server.logUseful for verifying file structure before applying heavier text processing.
bashANYtaillogs
bash
tail -n 50 server.logOften used with logs to inspect the most recent events.
bashANYtailfollowlogs
bash
tail -f /var/log/nginx/access.logUse `-f` to stream appended data in real time.
bashANYsedrangelines
bash
sed -n '100,120p' file.txt`sed -n` suppresses default output so only the requested range is printed.
bashANYawkrangenr
bash
awk 'NR>=100 && NR<=120' file.txtAwk's `NR` variable tracks the current line number.
Formatting and Cleanup
Normalize spacing, wrap text, and clean lines.
bashANYtrspacescleanup
bash
tr -s ' ' < input.txtGood for cleaning space-delimited text before further parsing.
bashANYsedtrimwhitespace
bash
sed 's/^[[:space:]]*//' file.txtCharacter classes make the expression portable across whitespace types.
bashANYsedtrimwhitespace
bash
sed 's/[[:space:]]*$//' file.txtUseful before committing scripts, YAML, or source files.
bashANYfmtwraptext
bash
fmt -w 72 README.txt`fmt` is useful for quickly wrapping plain text to a target width.
bashANYfoldwraplines
bash
fold -w 80 long-lines.txtUnlike `fmt`, `fold` wraps mechanically rather than reflowing paragraphs.
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