Use the more, less, and cat commands in Linux to view file contents

In Linux, the commands cat, more, and less can all be used to view file contents. cat displays the contents of the entire file at once, and can also connect multiple files for display. It is often used in conjunction with the redirection symbol and is suitable for situations where the file content is small. more and less are generally used to display file content that exceeds one screen, and provide page turning functions. Less is more powerful than more, providing commands such as page turning, jumping, and searching.

As we all know, the commands cat, more, and less in Linux can all be used to view file contents. The main differences are:

cat displays the contents of an entire file at once, and can also connect multiple files for display. It is often used in conjunction with the redirection symbol and is suitable for situations where the file content is small;

More and less are generally used to display file contents that exceed one screen and provide page turning function. More is more powerful than cat and provides paging display function. Less is more powerful than more and provides commands such as page turning, jumping, and searching. And both more and less support: use space to display the next page, and press b to display the previous page. The following describes these three commands in detail.

more file content or output viewing tool:

More is one of our most commonly used tools. It is most commonly used to display the output content, and then display it in pages according to the size of the window, and it can also prompt the percentage of the file;

Less View file content tool:

The less tool is also a tool for paging files or other outputs. It can be said to be an orthodox Linux tool for viewing file contents. It is extremely powerful. If you are a beginner, I recommend that you use less. Since there are too many contents in less, we will introduce the most commonly used ones.

In Linux, the commands cat, more, and less can all be used to view file contents. cat displays the contents of the entire file at once, and can also connect multiple files for display. It is often used in conjunction with the redirection symbol and is suitable for situations where the file content is small. more and less are generally used to display file content that exceeds one screen, and provide page turning functions. Less is more powerful than more, providing commands such as page turning, jumping, and searching.

cat

The cat command displays the contents of the entire file from top to bottom on the screen.

1. Command format

cat [選項]... [文件]...

2. Command function

Write [file] or standard input to standard output.

Cat has three main functions:

1). Display the entire file at once: cat filename

2). Create a file from the keyboard: cat > filename You can only create new files, you cannot edit existing files.

3). Merge several files into one file: cat file1 file2 > file

3. Common parameter list

• -A, --show-all is equivalent to -vET
• -b, --number-nonblank Number non-blank output lines
• -e is equivalent to -vE
• -E, --show-ends Display "$" at the end of each line
• -n, --number Number all output lines
• -s, --squeeze-blank Do not output multiple blank lines
• -t is equivalent to -vT
• -T, --show-tabs Show tab characters as ^I
• -u (ignored)
• -v, --show-nonprinting Use ^ and M- quoting, except for LFD and TAB
• --help Display this help message and exit
• --version show version information and exit

more

The more command will display the content page by page, making it easier for users to read page by page. The most basic command is to press the space key to go to the next page, and press the b key to go back one page. It also has a search string function. The more command reads the file from front to back, so the entire file is loaded at startup.

1. Command format

more [-dlfpcsu] [-num] [+/pattern] [+linenum] [file ...]

2. Command function

The more command has the same function as cat, which is to view the contents of a file. However, the difference is that more can view the contents of a file by page and also supports functions such as direct line jump.

3. Common parameter list

• -num The number of lines to display at a time
• -d Display friendly prompts at the bottom of each screen
• -l Ignore Ctrl+l (form feed). If this option is not given, the more command will pause after displaying a line containing the Ctrl+l characters and wait for commands.
• -f When calculating the number of lines, use the actual number of lines, not the number of lines after automatic line breaks (some single lines that are too long will be expanded to two or more lines)
• -p Clear the screen before displaying the next screen.
• -c Clear the screen from the top and then display.
• -s Compress consecutive blank lines in the file into one blank line for display.
• -u does not display underline
• +/ Search for the string first, then display from the end of the string
• +num Display from line num

4. Common operation commands

• Enter Go down n lines, need to be defined. The default is 1 line
• Ctrl+F Scroll down one screen
• Spacebar Scroll down one screen
• Ctrl+B Return to the previous screen
• = Output the current line number
• :f outputs the file name and the line number of the current line
• v calls the vi editor
• !Command calls Shell and executes the command
• q exitmore

less

The less tool is also a tool for paging files or other outputs. It can be said to be an orthodox Linux tool for viewing file contents, and its functions are extremely powerful. The usage of less is more flexible than that of more. When using more, we have no way to flip forward, we can only look backward. But if we use less, we can use the functions of the [pageup] [pagedown] keys to flip forward and backward, which makes it easier to view the contents of a file! In addition, less has more search functions, not only can you search downwards, but you can also search upwards.

1. Command format:

less [參數] 文件

2. Function:

less is similar to more, but with less you can browse the file at will, while more can only move forward but not backward, and less does not load the entire file before viewing it.

3. Command parameters:

• -b <buffer size> Set the buffer size
• -e Automatically exit when the file display is finished
• -f Force opening of special files, such as peripheral device codes, directories, and binary files
• -g only marks the last searched keyword
• -i Ignore case when searching
• -m displays percentage similar to more command
• -N Display line numbers for each line
• -o <filename> Save the output of less in the specified file
• -Q Do not use warning sound
• -s Display consecutive blank lines as one line
• -S If a line is too long, the excess part will be discarded
• -x <number> Display the "tab" key as a specified number of spaces
• / string: function to search down for "string"
• ? String: Function to search upwards for "string"
• n: repeat the previous search (related to / or ?)
• N: Repeat the previous search in reverse direction (related to / or ?)
• b Go back one page
• d Go back half a page
• h Display the help interface
• Q quits less command
• u Scroll forward half a page
• y scroll forward one line
• Spacebar scrolls one page
• Enter key scrolls one line

For example, when we display the contents of /etc/profile, we want it to display line numbers.

[root@localhost ~]# less -N /etc/profile

Summarize

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