The usage of grep in Linux is to search for lines of text that match a specific pattern and output the matching lines. The grep command has a variety of options and usages, allowing flexible search and matching operations according to different needs. Commonly used options are: 1. -i, ignore the case of characters when searching; 2. -n, display matching line numbers; 3. -c, count the number of matching lines; 4. -r, recursively search in the specified directory Search files under; 5. -l, only display file names containing matching items; 6. -v, reverse matching, output lines that do not contain matching items, etc.
#The operating system of this tutorial: linux6.4.3 system, Dell G3 computer.
The grep command is a commonly used text search tool in Linux/Unix environments. It uses regular expressions to search for lines of text that match specific patterns and outputs the matching lines. The grep command has a variety of options and usages, allowing flexible search and matching operations according to different needs.
Basic usage
The basic usage of the grep command is as follows:
grep [options] pattern [file...]
Among them, options are the options of the grep command, used to specify the search behavior; pattern is the search pattern, which can Use a regular expression to match text; file is the file name and specifies which files to search in.
Common options
The following are some common options for the grep command:
-i: Ignore case, ignore the case of characters when searching.
-n: Display matching line numbers.
-c: Count the number of matching lines.
-r: Recursively search for files in the specified directory.
-l: Show only file names that contain matches.
-v: Reverse matching, output lines that do not contain matching items.
-A num: Output the content after the matching item, num indicates the number of lines to be output.
-B num: Output the content before the matching item, num indicates the number of lines to be output.
-C num: Output the content before and after the match, num indicates the number of lines to be output.
Example usage
The following are some example usages of the grep command:
Search for lines containing the "grep" keyword in all files in the current directory:
grep grep *
Search for lines containing a specific string in the file and output the line number:
grep -n 'string' file.txt
Recursively search for keywords in the file in the directory:
grep -r 'pattern' /path/to/directory
Reverse match, output Lines that do not contain the keyword:
grep -v 'pattern' file.txt
Search for lines that contain the keyword but do not contain the keyword in a specific file:
grep 'pattern' file1.txt | grep -v -f file2.txt
Here is a more complex example, we will be in a directory Search for lines containing the "def" keyword in all Python files in its subdirectories, and output the line number and line content:
grep -n 'def' /path/to/directory/*.py
We can also use recursive search, for example, in the current directory and its subdirectories Search all files in the directory for lines containing the "import" keyword:
grep -r 'import' ./*
In addition, we can also use grep in conjunction with other commands, such as using pipes to pass the output to other commands for processing. Here is an example that uses grep to search a file for lines containing the "error" keyword, and passes the results to the less command for paged viewing:
grep 'error' file.txt | less
These examples are just a small sampling of what the grep command can do, The grep command also supports more complex regular expressions and more options. You can view more detailed grep command documentation by running the man grep command for more information and usage.
The above is the detailed content of What is the usage of grep in linux?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
How does the cost of ownership differ between Linux and Windows?
Jun 09, 2025 am 12:17 AM
Linux's cost of ownership is usually lower than Windows. 1) Linux does not require license fees, saving a lot of costs, while Windows requires purchasing a license. 2) Linux has low hardware requirements and can extend the service life of the device. 3) The Linux community provides free support to reduce maintenance costs. 4) Linux is highly secure and reduces productivity losses. 5) The Linux learning curve is steep, but Windows is easier to use. The choice should be based on specific needs and budget.
How to install Linux alongside Windows (dual boot)?
Jun 18, 2025 am 12:19 AM
The key to installing dual systems in Linux and Windows is partitioning and boot settings. 1. Preparation includes backing up data and compressing existing partitions to make space; 2. Use Ventoy or Rufus to make Linux boot USB disk, recommend Ubuntu; 3. Select "Coexist with other systems" or manually partition during installation (/at least 20GB, /home remaining space, swap optional); 4. Check the installation of third-party drivers to avoid hardware problems; 5. If you do not enter the Grub boot menu after installation, you can use boot-repair to repair the boot or adjust the BIOS startup sequence. As long as the steps are clear and the operation is done properly, the whole process is not complicated.
How to enable the EPEL (Extra Packages for Enterprise Linux) repository?
Jun 17, 2025 am 09:15 AM
The key to enabling EPEL repository is to select the correct installation method according to the system version. First, confirm the system type and version, and use the command cat/etc/os-release to obtain information; second, enable EPEL through dnfinstallepel-release on CentOS/RockyLinux, and the 8 and 9 version commands are the same; third, you need to manually download the corresponding version of the .repo file and install it on RHEL; fourth, you can re-import the GPG key when encountering problems. Note that the old version may not be supported, and you can also consider enabling epel-next to obtain the test package. After completing the above steps, use dnfrepolist to verify that the EPEL repository is successfully added.
How to choose a Linux distro for a beginner?
Jun 19, 2025 am 12:09 AM
Newbie users should first clarify their usage requirements when choosing a Linux distribution. 1. Choose Ubuntu or LinuxMint for daily use; programming and development are suitable for Manjaro or Fedora; use Lubuntu and other lightweight systems for old devices; recommend CentOSStream or Debian to learn the underlying principles. 2. Stability is preferred for UbuntuLTS or Debian; you can choose Arch or Manjaro to pursue new features. 3. In terms of community support, Ubuntu and LinuxMint are rich in resources, and Arch documents are technically oriented. 4. In terms of installation difficulty, Ubuntu and LinuxMint are relatively simple, and Arch is suitable for those with basic needs. It is recommended to try it first and then decide.
How to add a new disk to Linux
Jun 27, 2025 am 12:15 AM
The steps to add a new hard disk to the Linux system are as follows: 1. Confirm that the hard disk is recognized and use lsblk or fdisk-l to check; 2. Use fdisk or parted partitions, such as fdisk/dev/sdb and create and save; 3. Format the partition to a file system, such as mkfs.ext4/dev/sdb1; 4. Use the mount command for temporary mounts, such as mount/dev/sdb1/mnt/data; 5. Modify /etc/fstab to achieve automatic mount on the computer, and test the mount first to ensure correctness. Be sure to confirm data security before operation to avoid hardware connection problems.
Fixed the failure to upload files in Windows Google Chrome
Jul 08, 2025 pm 02:33 PM
Have problems uploading files in Google Chrome? This may be annoying, right? Whether you are attaching documents to emails, sharing images on social media, or submitting important files for work or school, a smooth file upload process is crucial. So, it can be frustrating if your file uploads continue to fail in Chrome on Windows PC. If you're not ready to give up your favorite browser, here are some tips for fixes that can't upload files on Windows Google Chrome 1. Start with Universal Repair Before we learn about any advanced troubleshooting tips, it's best to try some of the basic solutions mentioned below. Troubleshooting Internet connection issues: Internet connection
Where are system logs located in Linux?
Jun 24, 2025 am 12:15 AM
Logs in Linux systems are usually stored in the /var/log directory, which contains a variety of key log files, such as syslog or messages (record system logs), auth.log (record authentication events), kern.log (record kernel messages), dpkg.log or yum.log (record package operations), boot.log (record startup information); log content can be viewed through cat, tail-f or journalctl commands; application logs are often located in subdirectories under /var/log, such as Apache's apache2 or httpd directory, MySQL log files, etc.; at the same time, it is necessary to note that log permissions usually require s
What is the sudo command and when should I use it?
Jul 02, 2025 am 12:20 AM
sudo stands for "substituteuserdo" or "superuserdo", allowing users to run commands with permissions of other users (usually root). Its core uses include: 1. Perform system-level operations such as installing software or editing system files; 2. Accessing protected directories or logs; 3. Manage services such as restarting nginx; 4. Modify global settings such as /etc/hosts. When using it, the system will check the /etc/sudoers configuration and verify the user password, provide temporary permissions instead of continuously logging in as root, ensuring security. Best practices include: only when necessary, avoid blindly executing network commands, editing sudoers files with visudo, and considering continuous operations.
