Modify Content

Note: sed -i will change original file.

Overwrite

cat > file	Overwrite/create file
echo "text" > [file]	Overwrite/create file
echo "text" | tee [file]	Overwrite/create file and display
printf "Line 1\nLine 2" > [file]	Overwrite/create file with newlines.
awk -v text="some text" 'BEGIN{print text > "filename"}'	Overwrite/create file
echo "text" | dd of=file	Write "text" to file using dd, overwriting existing contents.

Insert

Strings

echo "text" >> [file]	Append "text" to the end of a file.
sed i\text	Before each line
sed a\text	After each line
sed '$ a\text' [file]	Use sed to insert "text" at the end of a file.
sed '$a text' file	Append "text" at the end of file.
sed '1i text' file	Insert "text" at the beginning of file
awk 'END {print "text"} 1' file > temp && mv temp [file]	Append "text" at the end of a file.

Lines

sed '1i\New line' [file]	Insert newline at beginning
sed '$a\New line' [file]	Append new line at the end
sed '/pattern/a\new line' file	Append new line after lines with pattern
sed G [file]	Adds blank line between lines (Double Space)
nl -ba file > temp && mv temp file	Add line numbers to each line.
awk '{print NR, $0}' file > temp && mv temp file	Add line numbers to each line.

Append

cat >> file	Append to file from stdin until EOF (Ctrl+D).
echo "text" | tee -a [file]	Append and display
printf "text" >> [file]	Append
awk -v text="more text" '{print $0 ORS text}' [file]	Append?

Replace / Remove

Replace Strings

sed 's/pattern/new/' [file]	Replace pattern with new in file.txt
sed 's/pattern/new/g' [file]	Replace all occurrences of "old" with "new".
sed 's/pattern/new/2' [file]	Replace 2nd pattern in a line.
sed '2 s/pattern/new/' [file]	Replace pattern on line 2
sed 1,5s/pattern/new/ [file]	Replace pattern on lines 1 to 5
sed /pattern/, /pattern2/s/old/new/	Replace between two patterns
sed $s/pattern/new/	Replace pattern on last line
sed 's/,/\n/g' file	Replace Commas with Newline
tr , '\n' < file	Replace Commas with Newline

Replaces occurrences of 'old_pattern' with 'new_pattern' and prints each line:

awk '{gsub(/old_pattern/, "new_pattern"); print}' [file]

Globally replace "old" with "new" in a file.

awk '{gsub(/old/, "new"); print}' [file] > temp && mv temp [file]

Finds and replaces text within a specified range:

awk '/start_pattern/, /end_pattern/ {gsub(/old_pattern/, "new_pattern"); print}' [file]

Use perl to replace "old" with "new" in a file, similar to sed:

perl -pi -e 's/old/new/g' [file]

Remove Strings

Command	Description
cut -f 1 -d $'\t' [file]	Suppressing Non-Printable Characters

Remove Lines

Patterns

sed '/pattern/d' file	Remove lines matching "pattern".
awk '!/pattern/' file > temp && mv temp file	Remove lines matching "pattern".
grep -v "pattern" file > temp && mv temp file	Use grep with -v to filter out lines matching "pattern".

Line Numbers

Command	Description
sed '/^9/d' [file]	Delete lines starting with 9
sed '1,3d' [file]	Delete lines 1 to 3

Blank Lines

sed '/^$/d' [file]	Remove blank lines.
sed 'n;d'	Remove blank lines between lines (Double Spaced) (assumes even numbered lines are blank)
awk 'NF' [file] > temp && mv temp [file]	Remove blank lines, keeping lines with at least one field.

Duplicate Lines

awk '!seen[$0]++' file > temp && mv temp file	Remove duplicate lines, preserving the order.
sort -u file > temp && mv temp file	Sort the file and remove duplicate lines, may change the original order.

Comment Lines

Removing lines that start with #. E ssentially this removes all the comments out of a file. This is good when examining a config file full of comments when you just want to see a certain line.

cat <file> |  grep -v ^\# | grep .

sed '/^#/d' <file>

Convert Case

tr '[:upper:]' '[:lower:]' < file > temp && mv temp file	Convert all text to lowercase.
tr '[:lower:]' '[:upper:]' < file > temp && mv temp file	Convert all text to uppercase.
awk '{print tolower($0)}' file > temp && mv temp file	Convert all text to lowercase using awk.
awk '{print toupper($0)}' file > temp && mv temp file	Convert all text to uppercase using awk.

Text Editors

vim file	Open file in Vim editor for editing. Save and exit with :wq.
nano file	Open file in Nano editor for editing. Save and exit with Ctrl+O, Ctrl+X.
emacs file	Open file in Emacs editor for editing. Save with Ctrl+x Ctrl+s and exit with Ctrl+x Ctrl+c.