Sed Command#

The sed command uses scripts to process text files. It can process and edit text files according to the instructions in the script. It is mainly used for automatically editing one or more files, simplifying repetitive operations on files, and writing conversion programs, among other things.

Syntax#

sed [OPTION]... {script-only-if-no-other-script} [input-file]...

Parameters#

• -n, --quiet, --silent: Suppress automatic printing of pattern space.
• -e script, --expression=script: Add the script to the commands to be executed.
• -f script-file, --file=script-file: Add the contents of the script file to the commands to be executed.
• --follow-symlinks: Follow symbolic links when doing in-place editing.
• -i[SUFFIX], --in-place[=SUFFIX]: Edit files in place; if a suffix is provided, make a backup of each edited file.
• -l N, --line-length=N: Specify the desired line length N for the l command.
• --POSIX: Disable all GNU extensions.
• -r, --regexp-extended: Use extended regular expressions in the script.
• -s, --separate: Treat input files as separate files, not a single continuous long stream.
• -u, --unbuffered: Load minimal amounts of input from the files and flush the output buffer more often.
• --help: Display help information.
• --version: Display version information.

Examples#

The content of the file.txt file is as follows.

Replace the first occurrence of the word unix with linux in each line of the file. If you want to save the changes, you need to use output redirection.

sed "s/unix/linux/" file.txt

# linux is great os. unix is opensource. unix is free os.
# learn operating system.
# linux linux which one you choose.
# linux is easy to learn.unix is a multiuser os.Learn unix .unix is a powerful.

Replace the second occurrence of the word unix with linux in each line.

sed "s/unix/linux/2" file.txt

# unix is great os. linux is opensource. unix is free os.
# learn operating system.
# unix linux which one you choose.
# unix is easy to learn.linux is a multiuser os.Learn unix .unix is a powerful.

Use the /g replacement flag to globally replace the specified sed command to replace all occurrences of the string in each line.

sed "s/unix/linux/g" file.txt

# linux is great os. linux is opensource. linux is free os.
# learn operating system.
# linux linux which one you choose.
# linux is easy to learn.linux is a multiuser os.Learn linux .linux is a powerful.

Replace all occurrences of the pattern past the second occurrence.

sed "s/unix/linux/2g" file.txt

# unix is great os. linux is opensource. linux is free os.
# learn operating system.
# unix linux which one you choose.
# unix is easy to learn.linux is a multiuser os.Learn linux .linux is a powerful

Enclose the first character of each word in parentheses and print it inside the parentheses.

echo "Welcome To The World" | sed "s/\(\b[A-Z]\)/\(\1\)/g"

# (W)elcome (T)o (T)he (W)orld

You can restrict the sed command to replace the string on a specific line number.

sed "3 s/unix/linux/g" file.txt

Daily Question#

References#