Ways to search for filenames and file contents using the grep command in Linux

Search for and display file names from a file

When you search from more than one file, it displays the file name by default:

The code is as follows:

grep "word" file name

grep root/etc/*

Sample output:

The code is as follows:

/etc/bash.bashrc:see "Man sudo_root" for details.

/ETC/CRONTAB:17 * * * * Root CD/&& run-parts--report/etc/cron.hourly

/ETC/CRONTAB:25 6 * * * Root test-x/usr/sbin/anacron | | (CD/&& run-parts--report/etc/cron.daily)

/ETC/CRONTAB:47 6 * * 7 root test-x/usr/sbin/anacron | | (CD/&& run-parts--report/etc/cron.weekly)

/ETC/CRONTAB:52 6 1 * * Root test-x/usr/sbin/anacron | | (CD/&& run-parts--report/etc/cron.monthly)

/etc/group:root:x:0:

grep:/etc/gshadow:permission denied

/etc/logrotate.conf:create 0664 Root Utmp

/etc/logrotate.conf:create 0660 Root Utmp

The first part of the start of each line is the filename (for example,/etc/crontab,/etc/group). Use the-l option to display only file names:

The code is as follows:

Grep-l "string" filename

Grep-l root/etc/*

Sample output:

The code is as follows:

/etc/aliases

/etc/arpwatch.conf

grep:/etc/at.deny:permission denied

/etc/bash.bashrc

/etc/bash_completion

/etc/ca-certificates.conf

/etc/crontab

/etc/group

You can also reverse the output; Use the-l option to output the file names of those files that do not match:

The code is as follows:

Grep-l "word" filename

Grep-l root/etc/*

Sample output:

The code is as follows:

/etc/apm

/etc/apparmor

/etc/apparmor.d

/etc/apport

/etc/apt

/etc/avahi

/etc/bash_completion.d

/etc/bindresvport.blacklist

/etc/blkid.conf

/etc/bluetooth

/etc/bogofilter.cf

/etc/bonobo-activation

/etc/brlapi.key

Find files based on file contents

Enter the following command:

The code is as follows:

grep ' String ' *.txt

grep ' Main (' *.c

grep ' #include ' *.c

grep ' getchar* ' *.c

Grep-i ' Ultra ' *.conf

Grep-ir ' Ultra ' *.conf

which

-I: Ignores patterns (matching strings valid, valid, valid) and input files (matching file.c file.c file. C) is case-insensitive.

-R: Recursively read all files in each directory.

Highlight match to the pattern

You can easily highlight patterns when searching for a large number of files:

The code is as follows:

$ grep--color=auto-ir ' GetChar (); ' *.c

Displays the file name and line number for the found pattern

You may need to display the file name and line number:

The code is as follows:

$ grep--color=auto-irnh ' GetChar (); ' *.c

which

-N: Adds a 1-based line number before each line in the output.

-H: Print file name for each match. This is the default option when you want to search for multiple files. (LCTT-H option forces hidden file names; the-L and-l options are used to display only matching/mismatched file names, while-H and-H are used to control the display/not display of file names before matching rows are displayed. )

The code is as follows:

$grep--color=auto-nh ' DIR ' *

Output Sample:

You can also use the Find command:

The code is as follows:

$ find. -name "*.C"-print | Xargs grep "Main ("