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ed Command

The ed command is a text editor used for text manipulation. It is the simplest text editing program in Linux, unlike other full-screen editing programs, ed can only edit one line at a time. Although not commonly used, ed commands are particularly useful for editing large files or for text editing within shell script programs. When ed is called with a file name parameter, a copy of the file is read into the editor's buffer. Changes are made to the copy, rather than directly to the file itself. Upon exiting ed, any changes not explicitly saved using the w command will be lost. There are two different modes of editing: command and input. When first invoked, ed is in command mode, where commands are read from standard input and executed to manipulate the contents of the editor's buffer.

Syntax

ed [options] [file]

Options

  • -G, --traditional: Run in compatibility mode.
  • -l, --loose-exit-status: Exit with zero status (normal termination) even if the command fails. This option is useful, for example, if setting ed as the editor for crontab.
  • -p, --prompt=STRING: By default, ed waits for user input on blank lines, this option allows the use of a specific string as a prompt.
  • -r, --restricted: Run in restricted mode.
  • -s, --quiet, --silent: Suppress diagnostics.
  • -v, --verbose: Verbose operation.
  • -h, --help: Display help information.
  • -V, --version: Display version information.

Exit Status

  • 0 indicates normal exit.
  • 1 indicates environmental issues, such as file not found, invalid flags, I/O errors, and so on.
  • 2 indicates a corrupt or invalid input file.
  • 3 indicates internal consistency errors (like a software bug) that cause ed to crash.

Examples

A complete editing example:

ed
a
My name is Titan.
And I love Perl very much.
.
i
I am 24.
.
c
I am 24 years old.
.
w readme.txt
q

Explanation:

ed                          # Activate the ed command
a                           # Tell ed that I want to edit a new file
My name is Titan.           # Enter the first line content
And I love Perl very much.  # Enter the second line content
.                           # Return to the ed command line state
i                           # Tell ed that I want to insert content before the last line
I am 24.                    # Insert I am 24. between My name is Titan. and And I love Perl very much.
.                           # Return to the ed command line state
c                           # Tell ed that I want to replace the last line's input content
I am 24 years old.          # Replace I am 24. with I am 24 years old., here replacing the last input content
.                           # Return to the ed command line state
w readme.txt                # Name the file readme.txt and save. If editing an existing file, only need to input w
q                           # Completely exit the ed editor

cat readme.txt
# My name is Titan.
# I am 24 years old.
# And I love Perl very much.

Daily Question

https://github.com/WindrunnerMax/EveryDay

References

https://www.computerhope.com/unix/ued.htm
https://www.runoob.com/linux/linux-comm-ed.html
https://www.geeksforgeeks.org/ed-command-in-linux-with-examples/