Master Essential Linux Shell Text Tools: Find, Grep, Awk, Sed & More

Linux Shell is a fundamental skill; despite its quirky syntax and lower readability compared to languages like Python, mastering it reveals many aspects of the Linux system and remains essential for everyday scripting.

Key tools for text handling in Linux include find, grep, xargs, sort, uniq, tr, cut, paste, wc, sed, and awk . The examples and parameters shown are the most common and practical. The author prefers one‑line commands and advises using Python for more complex tasks.

1. find – File Search

Search for *.txt and *.pdf files:

find . \( -name "*.txt" -o -name "*.pdf" \) -print

Regex search: find . -regex ".*\(\.txt|\.pdf\)$" Case‑insensitive regex: find . -iregex ".*\.txt$" Negate pattern (exclude txt files): find . ! -name "*.txt" -print Limit search depth (depth = 1): find . -maxdepth 1 -type f Search by type:

find . -type d -print   # directories only

find . -type f -print   # regular files

Search by time:

atime – access time (days)

mtime – modification time

ctime – metadata change time

find . -atime 7 -type f -print   # accessed in last 7 days

Search by size (e.g., larger than 2 KB): find . -type f -size +2k Search by permission: find . -type f -perm 644 -print Search by owner: find . -type f -user weber -print Actions after finding:

Delete: find . -type f -name "*.swp" -delete Execute (powerful -exec):

find . -type f -user root -exec chown weber {} \;

Note: {} is replaced by each matched file name.

find . -type f -mtime +10 -name "*.txt" -exec cp {} OLD \;

Combine multiple commands via a script: -exec ./commands.sh {} \; Output delimiters:

Default:

'
'

-print0

uses '\0' to handle spaces in file names.

2. grep – Text Search

Basic usage: grep match_pattern file Common options: -o output only matching part, -v invert match -c count matches -n show line numbers -i ignore case -l list matching file names

Recursive search (favorite for code): grep "class" . -R -n Match multiple patterns: grep -e "class" -e "virtual" file Use -z to output file names terminated by \0:

grep "test" file* -lZ | xargs -0 rm

3. xargs – Build Command Lines

Convert input lines to arguments, useful with grep or find: cat file.txt | xargs Convert multi‑line output to a single line: cat file.txt | xargs Convert a single line to multiple lines (e.g., three arguments per line): cat single.txt | xargs -n 3 Key options: -d define delimiter (default space, \n for lines) -n number of arguments per command line -I {} replace placeholder with each argument -0 use \0 as delimiter

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

4. sort – Sorting

Options: -n numeric sort, -d dictionary order -r reverse -k N sort by column N

sort -nrk 1 data.txt

sort -bd data   # ignore leading blanks

5. uniq – Remove Duplicate Lines

sort unsort.txt | uniq

Count occurrences: sort unsort.txt | uniq -c Show only duplicated lines: sort unsort.txt | uniq -d Compare specific fields with -s (start) and -w (width).

6. tr – Translate/Replace Characters

echo 12345 | tr '0-9' '9876543210'   # simple cipher

cat text | tr '\t' ' '   # tabs to spaces

Delete characters: cat file | tr -d '0-9' Complement set ( -c):

cat file | tr -c '0-9'

cat file | tr -d -c '0-9 
'

Compress repeated characters ( -s), often used to squeeze spaces: cat file | tr -s ' ' Character classes (e.g., [:lower:], [:digit:], [:space:]).

tr '[:lower:]' '[:upper:]'

7. cut – Column Extraction

cut -f2,4 filename

cut -f3 --complement filename   # all but column 3

Specify delimiter with -d: cat -f2 -d ";" filename Ranges: N- from field N to end -M first M fields N-M fields N through M

Units: -b bytes -c characters -f fields (delimiter‑based)

cut -c1-5 file   # first 5 characters

cut -c-2 file   # first 2 characters

8. paste – Merge Columns

paste file1 file2

Change delimiter (default tab) with -d:

paste file1 file2 -d ","

9. wc – Count Lines, Words, Bytes

wc -l file   # lines

wc -w file   # words

wc -c file   # bytes

10. sed – Stream Editing

Replace first occurrence: sed 's/text/replace_text/' file Global replace: sed 's/text/replace_text/g' file Edit file in place: sed -i 's/text/replace_text/g' file Delete empty lines: sed '/^$/d' file Use variables and double quotes for evaluation:

p=pattern; r=replace; echo "a line with $p" | sed "s/$p/$r/g"

11. awk – Data‑Stream Processing

Structure: awk 'BEGIN{...} { ... } END{...}' file Built‑in variables: NR (record number), NF (field count), $0 (whole line), $1, $2, … awk '{print $2, $3}' file Count lines: awk 'END{print NR}' file Sum first column: awk '{sum+=$1} END{print sum}' file Pass external variable: var=1000; awk -v v=$var '{print v}' file Set field separator: awk -F: '{print $NF}' /etc/passwd Read command output:

awk '{"grep root /etc/passwd" | getline out; print out}'

Implement head and tail:

awk 'NR<=10{print}' file   # head

awk '{buf[NR%10]=$0} END{for(i=0;i<10;i++) print buf[i]}' file   # tail

Common functions: index(), sub(), match(), length(), printf().

12. Iterating Lines, Words, and Characters

While‑read loop:

while read line; do echo "$line"; done < file.txt

Awk alternative: cat file.txt | awk '{print}' Iterate words in a line: for word in $line; do echo $word; done Iterate characters using Bash substring syntax:

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