Grep command is used to search text or string in any text file. Grep command in Linux stands for “global search for the regular expression”. The text for which search is executed using Grep command is called regular expression.
Syntax
grep <options> <pattern> /path/to/file
Example
grep -i “infojinx” /home/test.txt
This command searches for word infojinx in test.txt file in home folder. Use -i makes search ignore case sensitivity.
grep command in Linux has multiple options for search few of them are as below
| Options | Description |
| -i | searches ignoring case |
| -l | search displays name of file matching pattern |
| -n | searches and displays matching line with its number |
| -c | searches and displays only count of lines where pattern matches |
| -v | inverse match i.e. display line which does not match pattern searched for |
| -w | Matches word i.e. matches string even if it exists as substring |
| -h | Displays on matched line and not file name |
Linux – Grep command with examples
Search for file using grep command
Grep command can be used to search file in a folder using below syntax
Syntax
grep file_name /path/for/search
Example
grep test.txt /home
To ignore case sensitivity during file search use switch -i
grep -i test.txt /home
Search for string in a file using grep command
Grep command can also be used to search any string in file or files. Note: grep will only search for string given if it exist as word and ignore this string if its part / substring of a word
Syntax
grep “string_to_search” file_name
Example
grep “infojinx” test.txt
The above command will search for word infojinx in test.txt file
Search for string in a file using grep command matching string even if it exists as part of word
Syntax
grep -w “string_to_search” file_name
Example
grep -w “infojinx” test.txt
The above command will search for word infojinx in test.txt file, not ignoring it even if it is part of a word.
Search and display count of matches found in file
Using this command one can search for lines which matches and display count of matching line found.
Syntax
grep -c “string_to_search” file_name
Example
grep -c “infojinx” test.txt
Search and display only matched string
By default grep searches and shows content of entire line where a match is found. But you can use switch -o to see only matched string.
Syntax
grep -o “string_to_search” file_name
Example
grep -o “infojinx” test.txt
Search with inverted pattern
By using switch -v pattern of search will be inverted, i.e. lines which do not match with the searched pattern will be displayed.
Syntax
grep -v “string_to_search” file_name
Example
grep -v “infojinx” test.txt
Search and display line with line number where match for string is found
Using switch -n search will be made for matching string. Display will done of line number followed by line.
Syntax
grep -n “string_to_search” file_name
Example
grep -n “infojinx” test.txt
Search for string at specific position in line
To search for a string at the start of a line use special character “^”.
Syntax
grep “^string_to_search” file_name
Example
grep “^infojinx” test.txt
Above command will display all lines where infojinx is used in start of line.
To search for a string at the end of a line use special character “$”.
Syntax
grep “string_to_search$” file_name
Example
grep “infojinx$” test.txt
Above command will display all lines where infojinx is used at end of line.
Search for special character in file
To search for any special character in a file, you need to escape them using “\” (backslash)
Syntax
grep “\special character” file_name
Example
grep “\*” test.txt
This command will search for “*” in test.txt file.
Search for a range or set of characters in file
To search for a range of characters or set of characters use pair of [].
Syntax
grep “[string or range of characters]” file_name
Example
grep “[amn]” test.txt
This will search for characters amn and line will be displayed if any of them are found.
grep”[a-d]” test.txt
This command will search any character from a to d and display line if any of them are found.
