Master Essential Linux Shell Tools: find, grep, awk, sed & More

Linux shell is a fundamental skill; mastering its core utilities greatly enhances text processing and system navigation.

1. find – File Search

Common examples:

<code>find . \( -name "*.txt" -o -name "*.pdf" \) -print</code>

<code>find . -regex ".*\(\.txt|\.pdf\)$"</code>

<code>find . ! -name "*.txt" -print</code>

<code>find . -maxdepth 1 -type f</code>

Search by type, time, size, permissions, user, etc. Example – files accessed in the last 7 days:

<code>find . -atime 7 -type f -print</code>

Delete all swap files:

<code>find . -type f -name "*.swp" -delete</code>

Execute actions with

-exec

:

<code>find . -type f -user root -exec chown weber {} \;</code>

{} is replaced by each matched filename.

2. grep – Text Search

Basic usage and useful options:

-o: output only matching parts

-v: invert match

-c: count matches

-n: show line numbers

-i: ignore case

-l: list matching file names

<code>grep -c "text" filename</code>

<code>grep "class" . -R -n</code>

<code>grep -e "class" -e "virtual" file</code>

<code>grep "test" file* -lZ | xargs -0 rm</code>

3. xargs – Build Command Lines

Convert input into command arguments, often combined with

grep

or

find

:

<code>cat file.txt | xargs</code>

<code>cat single.txt | xargs -n 3</code>

Key options:

-d: define delimiter (default space, \n for lines)

-n: number of arguments per command line

-I {}: replace placeholder with input

-0: use \0 as delimiter

<code>cat file.txt | xargs -I {} ./command.sh -p {} -1</code>

<code>find source_dir/ -type f -name "*.cpp" -print0 | xargs -0 wc -l</code>

4. sort – Sorting

Options:

-n: numeric sort

-d: dictionary order

-r: reverse

-k N: sort by column N

<code>sort -nrk 1 data.txt</code>

<code>sort -bd data   # ignore leading blanks</code>

5. uniq – Remove Duplicate Lines

<code>sort unsort.txt | uniq</code>

<code>sort unsort.txt | uniq -c   # count occurrences</code>

<code>sort unsort.txt | uniq -d   # show duplicates only</code>

6. tr – Translate Characters

Common uses:

<code>echo 12345 | tr '0-9' '9876543210'</code>

<code>cat text | tr '\t' ' '</code>

<code>cat file | tr -d '0-9'   # delete digits</code>

<code>cat file | tr -c '0-9'   # keep only digits</code>

<code>cat file | tr -s ' '   # squeeze spaces</code>

7. cut – Column Extraction

<code>cut -f2,4 filename</code>

<code>cut -f3 --complement filename</code>

<code>cut -f2 -d ";" filename</code>

8. paste – Merge Columns

Combine files side‑by‑side, default delimiter is a tab; use

-d

to change:

<code>paste file1 file2 -d ","</code>

9. wc – Count Lines, Words, Bytes

<code>wc -l file   # lines</code>

<code>wc -w file   # words</code>

<code>wc -c file   # bytes</code>

10. sed – Stream Editing

Replace first occurrence:

<code>sed 's/text/replace_text/' file</code>

Global replacement:

<code>sed 's/text/replace_text/g' file</code>

In‑place edit:

<code>sed -i 's/text/replace_text/g' file</code>

Delete empty lines:

<code>sed '/^$/d' file</code>

11. awk – Powerful Text Processor

Basic script structure:

<code>awk 'BEGIN{...} { ... } END{...}' file</code>

Print current line:

<code>awk '{print}' file</code>

Print specific fields:

<code>awk '{print $2, $3}' file</code>

Count lines:

<code>awk 'END{print NR}' file</code>

Sum a column:

<code>awk '{sum+=$1} END{print sum}' file</code>

Set field separator:

<code>awk -F: '{print $NF}' /etc/passwd</code>

Read command output:

<code>awk '{"grep root /etc/passwd" | getline cmd; print cmd}'</code>

12. Iterating Over Files

Line‑by‑line loop:

<code>while read line; do echo $line; done < file.txt</code>

Word iteration:

<code>for word in $line; do echo $word; done</code>

Character iteration (bash substring):

<code>for ((i=0;i<${#word};i++)); do echo ${word:i:1}; done</code>

Source: 大CC, http://www.cnblogs.com/me115/p/3427319.html