The question is what can you do with just the first byte of your various IP addresses, and why ip2 is set to the same value as ip1. This is done that way because the -o options of grep makes it output the match and you don't want the "inet " bit to be printed even if it is important to the match. So (?<=inet )+ matches a non-empty sequence of characters that aren't periods ( +), if they follow "inet ", in other words the first byte of the various IP addresses of your network interfaces because ip address show output lines such as inet 127.0.0.1/8 scope host lo. e option indicates an expression in the grep command.-P means that grep should use the Perl regexp syntax and in Perl, (?<=pattern) is a " zero-width positive look-behind assertion", in other words, an anchor that should appear before the match itself. Grep -e command allows you to use multiple patterns at once. Search for multiple patterns with single command using grep command Note: Any character at the end counts including spaces.Ģ0. You have to put dollar sign($) in the end of pattern. You can also search specific lines that end with a pattern using grep command. grep command to search lines that end with matching pattern It does not print other lines that contain the matching pattern elsewhere. You can search specific lines that start with a pattern using grep command. Search lines that start with pattern using grep command They also print the lines containing the match. grep -C n prints the n lines before and after the match.grep -B n prints the n lines before the match.grep -A n prints the n lines after the match.You can print the lines that come before and after the matching patterns. Print lines before or after pattern match $ grep -h pattern file_name1 file_name2 file_name3ĪLSO READ: 30 nmap command examples in Linux 17. grep command normally shows file names when there are matched patterns in multiple files. You can use any commands that search in multiple files. Grep -h command hides the file name in the output. Hide filename of the matched pattern with grep command By default, grep command only prints file names if there are multiple files. Grep -H command prints the every line with file name that contain the matching patterns. Print filename along with the match in grep command Grep -f command allows you to take pattern from file. Take pattern from file using grep command Note: If there are matched patterns in multiple files, it will print N lines of each file.ġ4. The first NUM lines with the match will only be printed. It takes a number(NUM) as an argument along with it to print NUM lines. grep command normally prints all matched patterns in a file. Grep -m command prints the limited number of line that contains the matching patterns. Stop reading a file after NUM matching lines with grep command $ grep -L pattern *ĪLSO READ: 15 most used chown command in Linux 13. You can print the names of file that do not contain the matching patterns using grep -L command. This is just the opposite version of previous command. Print files name having unmatched patterns using grep command In the above output, -r and * are used to search files in the current directory and its sub-directories.ġ2. Note: You can combine options in grep command to get the desired result. It is a useful command when you want to know file names only. Grep -l command prints the file names only that contain the matching patterns instead of printing the whole line. grep command to print list of matching files only It also prints the exact path for the file in sub-directories. This command searches the matches in all files in the current directory including its sub-directories. grep command to search in directories and sub-directories It does not search files that are in the sub-directories. Grep command allows you to search all files in the current directory using asterisk(*). Search all files in directory using grep command Search for multiple patterns with single command using grep commandĪLSO READ: 10 examples to generate SSH key in Linux (ssh-keygen)ĩ. Print only the matched pattern with grep command Count the number of lines using grep command grep command to search whole words (exact word) only Perform case sensitive search using grep command
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