Egrep vs Fgrep: Difference and Comparison

Egrep and Fgrep are text inspecting utilities that toil on the command line, where the two commands are registered in the toolbox as a grep command that is utilized to find possible matches within files or data locations.

Both Egrep and Fgrep are exceptionally similar in function and origin, yet they are extraordinarily different too.

Key Takeaways

1. egrep allows for more advanced pattern searches using regular expressions.
2. fgrep focuses on fixed-string searches, providing faster results.
3. Users should choose based on search requirements, as egrep is more versatile, but fgrep is quicker.

Egrep vs Fgrep

Grep (Global Regular Expressions Print) is a UNIX command that is used to search files according to the given regular expression and display the matching lines. Egrep (Extended Grep) is a variant of grep that is more efficient and faster. It searches a file line by line to find and display the machining lines.

Egrep is essentially a smaller and faster version of grep with some added functionality and different default behaviors. Egrep looks for files in any of the specified directories, where this option is equivalent to “–include=DIRS,” moreover, without this option, only files matching the specified patterns and their directory names are found.

Fgrep, is a command-line tool that searches for text in any number of files and documents. Fgrep is a very useful command-line tool that can be used to search through large files for a given string.

Moreover, the “f” flag, when present, causes all files except those with names beginning with. “” to be ignored.

Comparison Table

Parameters of Comparison	Egrep	Fgrep
Elucidation	Egrep takes its input from standard input, which can be achieved by piping the content of a file through it.	Fgrep takes its input from a file that must be specified in a command-line argument.
Expression Forage	Egrep employs extended regular expressions.	Fgrep employs non-extended regular expressions.
Rapidity	It has low rapidity.	It has high rapidity.
String Modes	It explores a string or list that accumulates multiple modes.	It does not explore a string or list that accumulates multiple modes.
Illustration	$ egrep -E “5|[[:space:]]*5” ./file.txt.	$ fgrep -F “5|[[:space:]]*5” ./file.txt.

What is Egrep?

Egrep is a command-line tool for searching through text files, much like grep. Some options to Egrep can seem weird or labored, but they have a purpose.

The -E option allows the search string to match anywhere in a target line. For instance, some Egrep is much faster if the user uses it with the -I option.

However, If the user doesn’t use it then, it takes a long time to run and generates a lot of unnecessary output.

Egrep operates on files in text format and takes different options that allow it to work with regular expressions. For instance, | egrep -i ‘(.+1) |’ command displays lines that contain the phrase, in one place and with the pattern in all lowercase and | egrep -I ‘(now.*c#na)’ internet_archiving is the Internet Archive that is a popular place to archive old files, such as newsletters, and photographs, moreover, this command will capture all lines from the output of any news program.

Egrep can search for substrings within one or multiple files or in standard input and save results to a file. For instance, egrep “pattern” *|sort >file.txt, file2.txt will store all lines matching “pattern” in “file.txt,” egrep -oP “(pattern|another)” *|sort >file.txt, and file2.txt will store matches of pattern or another in “file.txt.”

The Regular expression searches may be more efficient in some cases by not outputting matches for lines containing no matches.

For instance, “eq” tends to match the first character in each line, so it’s useful for finding matching words in files where the second word is only used once or twice.

If the user wants to find every occurrence of a substring, then utilize egrep “-ic” as a shortcut.

What is Fgrep?

Fgrep command is a friendly, efficient grep efficacy that uses Google-like search to find text. It works in both the bash shell and zsh.

Moreover, Fgrep highlights each match in red, so the user can see exactly what is being searched as well as what has been found to highlight automatically after the user makes a change, where the syntax is fgrep “string with spaces” *.

Fgrep can be installed by typing the two commands in the terminal that are Sudo apt-get install fgrep, and Sudo apt-get install zsh.

However, for installing zsh once Fgrep is installed, press Ctrl+Space in the terminal to invoke its “Google-like search” moreover, Fgrep works only with bash and zsh.

The Fgrep command has a few extra features that may be useful for the user. Using Fgrep, the user can see all the lines that are matched by their given search query, and the user has the option to either keep or delete them.

Moreover, it can also be used to filter input displayed on terminal screens by specifying output, such as lines with words containing letters A through Z.

Main Differences Between Egrep and Fgrep

1. The elucidation of Egrep lay hold of its data from quality data, which can be attained by piping the content of a file through it, whereas, Fgrep get hold of data from a file that must be particular in a command-line argument.
2. The expression forage of Egrep takes on extended regular expressions, whereas the expression forage of Fgrep takes on non-extended regular expressions.
3. The rapidity of Egrep is low, whereas the rapidity of Fgrep is high.
4. The Egrep inspects a string or list that comprises multiple modes, whereas the Fgrep does not inspect a string or list that comprises multiple modes.
5. The illustration of Egrep $ egrep -E “5|[[:space:]]*5” ./file.txt, wheres, the illustration of Fgrep $ fgrep -F “5|[[:space:]]*5” ./file.txt.

References

1. https://dl.acm.org/doi/pdf/10.1145/1473195.1473196
2. https://www.cs.arizona.edu/sites/default/files/TR94-17.pdf

Last Updated : 13 July, 2023