How to view linux files

How to view linux files

Command to view file contents:

cat Start displaying the content from the first line, and Output all contents

tac Display the contents in reverse order from the last line, and output all contents

more Depending on the window size, the actual file content page by page

less and more is similar, but its advantage is that you can page forward and search for characters

head only displays the first few lines

tail only displays the last few lines

nl is similar to cat -n, output the line number when displaying

tailf is similar to tail -f

(Online video tutorial sharing: linux video tutorial)

1.cat and tac

The function of cat is to continuously output the contents of the file on the screen starting from the first line. When the file is large and the number of lines is relatively large, and the screen cannot accommodate all of it, only part of the content can be seen.

cat syntax: cat [-n] file name (-n: when displayed, output the line number together)

The function of tac is to reverse the file starting from the last line and read the content data output to the screen. We can find that tac is actually cat written in reverse.

tac syntax: tac file name.

2.more and less (commonly used)

The function of more is to start the file from the first line and output the file content appropriately according to the size of the output window. When the entire page cannot be output, you can use the "Enter key" to scroll down a line and the "Space bar" to scroll down a page. To exit the viewing page, please press the "q" key. In addition, more can also be used with the pipe character "|" (pipe), for example: ls -al | more

more's syntax: more file name

Enter n lines down, needs to be defined , the default is 1 line;

Ctrl f scrolls down one screen;

Space bar scrolls down one screen;

Ctrl b returns to the previous screen;

= Output the line number of the current line;

:f Output the file name and the line number of the current line;

v Call the vi editor;

! The command calls Shell , and execute the command;

q exit more

The function of less is similar to more, but using more cannot turn pages forward, only backward.

less can use the [pageup] and [pagedown] keys to turn pages forward and backward, which seems more convenient.

less syntax: less file name

less also has a function that allows you to search for the content you want to find in the file. Suppose you want to find whether there is a weblogic string in the passwd file. , then you can do it like this:

[root@redhat etc]# less passwd

Then enter:

/weblogic

Enter

If there is a weblogic string at this time, Linux will highlight the character.

To exit the viewing page, please press the "q" key.

3.head and tail

head and tail are usually used when only the first few lines or the last few lines of the file need to be read. The function of head is to display the first few lines of the file

The syntax of head: head [n number] file name (number displays the number of lines)

The function of tail is exactly the opposite of head, which only displays The last few lines of content

The syntax of tail: tail [-n number] File name

4.nl

nl function and cat -n Same, it also outputs the entire content from the first line and displays the line number

nl syntax: nl file name

5.tailf

The tailf command is almost equivalent to tail -f. Strictly speaking, it should be more similar to tail --follow=name. It can also continue to track when the file is renamed, which is especially suitable for following the growth of a log file.

Different from tail -f, if the file does not grow, it will not access the disk file.

tailf is particularly suitable for tracking log files on portable computers because it saves power and reduces disk access.

The tailf command is not a script, but a binary executable file compiled with C code. Some Linux installations do not have this command.

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