Difference Between Egrep and Fgrep

Egrep vs Fgrep

Egrep and fgrep are both part of the grep family of commands. Both egrep and fgrep are used in Linux as user commands to make the search easier for delving into plain text files in thousands of lines. Both commands are DOS-based text searching utilities and search files, directories, and directory trees for a specific text or words.

Grep is the base command for both egrep and fgrep. “Grep” stands for “global regular expression print.” Grep supports regular expression commands in searching words and terms.

Egrep is an extension of the grep command, a user command to search a string of characters in lines and multiple patterns inside a text file. Also known as extended grep, it searches for one of the more patterned arguments. Egrep is used when the document is characterized as an “extended expression.” In using this command, special characters like +, ?, !, & and other characters and useful sequences will yield results instead of displaying a syntax error. This happens because the egrep command interprets them as part of a regular expression.

Expressions like the plus sign, question mark, vertical bar, and parentheses are often used as operators that help in specifying results. The expression is placed after the search term or regular expression. The following describes the function of the operators:

Regular expression and a plus sign yield one or more results of the regular expression.
Regular expression before a question mark gives matches zero or one matches of the given search term.
A vertical bar is used to separate multiple regular expressions or search terms.
Parentheses are used to enclose and group a regular expression or words.

In encoding this command “d” in Linux, it is expressed as “grep-e,” ??egrep, or egrep plus for the word or terms to search within the file. There is no limit to how many search words that can be included.

Meanwhile, the fgrep is an extension of egrep. In Linux, it is denoted as “grep-f” and also known as a fixed-string grep. It is similar to grep since it does not recognize or interpret regular or any special expression or characters. Since it does not understand the extended capabilities of regular expression, it bypasses these characters during a search. It only returns match words and terms and nothing else.

Fgrep interprets the documents as a list of fixed strings. Its search process is very fast compared to the other commands because it uses the Aho–Corasick string-matching algorithm.

Summary:

1.Both egrep and fgrep are derived from the base grep command. The “egrep” stands for “extended grep” while the fgrep stands for “fixed-string grep.”
2.An egrep command is used to search for multiple patterns inside a file or other kind of data repository while frgrep is used to look for strings.
3.The term “egrep” is commonly expressed as “grep-e” while “fgrep” is encoded as “grep-f.”
4.The egrep command allows the use of extended regular expressions while grep only searches for the matching word or term that the user specified in the command. The frep doesn’t recognize or understand regular or extended regular expression.
5.Compared to the other search commands, the search process for fgrep is very fast since it is only concerned with the provided search word.
6.The egrep command usually uses operators in order to yield a more progressive or specific search research. A plus sign and the question mark deal with single, regular expressions or search terms. On the other hand, vertical bars and parentheses are used for multiple, regular expressions with opposing functions. The vertical bar separates the expressions while the parentheses operator groups them.

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