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fgrep command is optimal for quick search of ASCII text files for a specific string. It is especially valuable for search in large volumes of text. If you need to search an exact word (or any exact substring) it is unwise to use generic complex pattern matching algorithm for this task. It's like sending tanks to capture unarmed native village. fgrep is designed to be a fast exact string matching tool and it uses special string matching algorithm to achieve that.
fgrep can be invoked either directly or via option -F in a regular grep:grep -F [-c| -l| -q] [-bhinsvwx] -e string_list... [-f string_file]... [file...] fgrep [-c| -l| -q] [-bhinsvwx] -e string_list... [-f string_file]... [file...]
The command uses the string provided on the command line to search the file_list for a match. fgrep searches the file_list for each string listed. In case you use option -f , multiple strings can be stored in file.
The most popular options include:
|-b||Displays the block number in which the pattern was found before the line that contains the matching pattern.|
|-c||Displays only a total count of matching lines for each file processed.|
|-e -string||-e string The -estring option has the same effect as the string
operand, but is useful when string begins with the hyphen or you need to specify several strings to search.
There are two ways to specify several strings to search:
If the strings overlap, the order of evaluation of strings is unspecified.
|-f file||Read in the strings to search for from file. This allows you to create a file containing all of the strings you want fgrep to search for in the file_list or standard input.|
|-h||Suppress the displaying of filenames which precede lines that match the specified patterns when multiple files are searched.|
|-i||Ignore the difference between uppercase and lowercase characters during comparisons.|
|-l||Displays only the names of the files containing the specified pattern. The lines containing the patterns are not displayed.|
|-n||Displays the line number before each line containing the pattern.|
|-v||Displays only the lines that do not match the pattern. The v command in the ex editor performs the same type of function. It is an exception search. Search for every line except the ones containing the given pattern.|
|-x||Displays only those lines matched in their entirety.|
-e pattern_list [file...]
/usr/bin/fgrep [-bchilnsvx] -f file [file...]
/usr/bin/fgrep [-bchilnsvx] pattern [file...]
/usr/xpg4/bin/fgrep [-bchilnqsvx] -e pattern_list [-f file] [file...]
/usr/xpg4/bin/fgrep [-bchilnqsvx] [-e pattern_list] -f file [file...]
/usr/xpg4/bin/fgrep [-bchilnqsvx] pattern [file...]
The fgrep (fast grep) utility searches files for a character string and prints all lines that contain that string. fgrep is different from grep(1) and from egrep(1) because it searches for a string, instead of searching for a pattern that matches an expression. fgrep uses a fast and compact algorithm.
The characters $, *, [, ‸, |, (, ), and \ are interpreted literally by fgrep, that is, fgrep does not recognize full regular expressions as does egrep. These characters have special meaning to the shell. Therefore, to be safe, enclose the entire string within single quotes (´).
If no files are specified, fgrep assumes standard input. Normally, each line that is found is copied to the standard output. The file name is printed before each line that is found if there is more than one input file.
The following options are supported for both /usr/bin/fgrep and /usr/xpg4/bin/fgrep:
The following options are supported for /usr/xpg4/bin/fgrep only:
The following operands are supported:
See largefile(5) for the description of the behavior of fgrep when encountering files greater than or equal to 2 Gbyte ( 231 bytes).
See environ(5) for descriptions of the following environment variables that affect the execution of fgrep: LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH.
The following exit values are returned:
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
Ideally, there should be only one grep command, but there is not a single algorithm that spans a wide enough range of space-time tradeoffs.
Lines are limited only by the size of the available virtual memory.
The /usr/xpg4/bin/fgrep utility is identical to /usr/xpg4/bin/grep -F (see grep(1)). Portable applications should use /usr/xpg4/bin/grep -F.
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