CentOS File Content Query command

Document Content Query

Cat: displays the file content starting from the first line.

Tac: displays the file content starting from the last line

Nl: displays the row number.

More: displays the file content on one page.

Less: similar to more, but it can flip the page forward

Head: only the first few lines

Tail: only the last few rows

Touch: file creation and modification of file time

Cat (concatenate)

Syntax: cat [-AbEnTv]

Options and parameters:

-A: equivalent to the Integration parameter of-vET

-B: list the row numbers. Only the row numbers are displayed for non-blank rows.

-N: the output line number. Both blank and non-blank fields are listed.

-E: display the ending line break characters ￥

-V: lists some unreadable special characters.

-T: press the Tab key to display it with consumer I.

Example:

[root@localhost tmp]# cat /etc/issueCentOS release 5.10 (Final)Kernel \r on an \m[root@localhost tmp]# cat -n /etc/issue     1  CentOS release 5.10 (Final)     2  Kernel \r on an \m     3[root@localhost tmp]# cat -A /etc/issueCentOS release 5.10 (Final)$Kernel \r on an \m$$

Add row number and print (nl)

Syntax: [root @ www ~] # Nl [-bnw] File

Options and parameters:

-B: Specifies the row number in two ways:

-Ba: indicates that the row number (similar to cat-n) is also listed no matter whether the row is empty or not );

-Bt: if there are blank rows, do not list the row numbers (default value) for the empty rows );

-N: Used to list row numbers. There are three methods:

-Nln: the row number is displayed on the leftmost side of the screen;

-Nrn: the row number is displayed on the rightmost side of its own column without 0;

-Nrz: the row number is displayed on the rightmost side of its own column with a value of 0;

-W: The number of digits occupied by the row number column.

Example

[Root @ www ~] # Nl/etc/issue 1 CentOS release 5.3 (Final) 2 Kernel \ r on an \ m this file actually has three rows, the third row is blank (no bytes ), because it is a blank line, the nl will not add a line number. [root @ www ~] # Nl-B a/etc/issue 1 CentOS release 5.3 (Final) 2 Kernel \ r on an \ m 3 [root @ www ~] # Nl-B a-n rz/etc/issue000001 CentOS release 5.3 (Final) 000002 Kernel \ r on an \ m000003 automatically add 0 in the position of your own bar ~ The default field is six digits. If you want to change it to three digits? [Root @ www ~] # Nl-B a-n rz-w 3/etc/issue001 CentOS release 5.3 (Final) 002 Kernel \ r on an \ m003

Syntax: more | less file

More:

Blank key (space): Indicates turning one page down;

Enter: Indicates turning "One Line" down 』;

/String: searches for the keyword "string" in the displayed content;

: F: displays the file name and the number of currently displayed rows immediately;

Q: The system immediately leaves more and the file content is no longer displayed.

B or [ctrl]-B: Indicates turning back the page. However, this action is only useful to files and useless to pipelines.

Less:

Blank key: Scroll down a page;

[Pagedown]: Scroll down a page;

[Pageup]: returns a page up;

/String: searches down for the "string" function;

? String: the "string" search function is enabled;

N: Repeat the previous search (and/or? Related !)

N: Repeat the previous search (and/or? Related !)

Q: Leave the less program;

Example:

[root@localhost tmp]# more /etc/man.config ## Generated automatically from man.conf.in by the……..# and to determine the correspondence between extensions and decompressors.## MANBIN                /usr/local/bin/man#--More--(31%)

Extract the first few rows (head)

Syntax: head [-nnumber] File

Options and parameters:

-N: Followed by a number, indicating the number of rows

The default value of number is 10. When number is a negative number, it indicates listing all the preceding rows but not including the following number rows.

Remove the following lines (tail)

Syntax: tail [-nnumber] File

Options and parameters:

-N: Followed by a number, indicating the number of rows

The default value of number is 10. When number is positive (+ number), it indicates that the file will be listed after number.

File modification time | create a new file (touch)

Time attribute

Mtime (modificationtime): This time is updated when the file content data changes. The content data refers to the file content, excluding the file permissions and attributes.

Ctime (Statetime): This time is updated when the file state (permission and attribute) is changed.

Atime (accesstime): This time will be modified when the file content is used.

Example:

[Root @ localhost ~] # Ls-l -- time-style = long-iso/etc/man. by default, config modifies mtime-rw-r -- 1 root 4617/etc/man. config [root @ localhost ~] # Ls-l -- time = ctime -- time-style = long-iso/etc/man. config-rw-r -- 1 root 4617/etc/man. config [root @ localhost ~] # Ls-l -- time = atime -- time-style = long-iso/etc/man. config-rw-r -- 1 root 4617/etc/man. config

Syntax: touch [-acdmt] File

Options and parameters:

-A: only modify the access time atime

-C: only the time when the file is modified. If the file does not exist, no new file is created.

-D: the date to be modified. You can also use-date = "time or date"

-M: only modify mtime

-T: The time to be modified.

Main functions:

Create an empty file

Modify the file date (mtime, atime)

Example:

[Root @ localhost tmp] # cp-a/etc/man. config. /newman. config [root @ localhost tmp] # ls-l -- time-style = long-iso newman. config specifies the time format-rw-r -- 1 root 4617 newman. config [root @ localhost tmp] # touch-m-t 0709150203 newman. config // only modify mtime [root @ localhost tmp] # ls-l -- time-style = long-iso newman. config-rw-r -- 1 root 4617 newman. config [root @ localhost tmp] # ls-l -- time = atime -- time-style = long-iso newman. config // only modify atime-rw-r -- 1 root 4617 newman. config [root @ localhost tmp] # touch-a-t 0809150203 newman. config [root @ localhost tmp] # ls-l -- time = atime -- time-style = long-iso newman. config-rw-r -- 1 root 4617 newman. config [root @ localhost tmp] # [root @ localhost tmp] # touch-d "2 days ago" newman. config // atime and mtime [root @ localhost tmp] # ls-l -- time = atime -- time-style = long-iso newman are modified by default. config-rw-r -- 1 root 4617 newman. config [root @ localhost tmp] # ls-l -- time-style = long-iso newman. config-rw-r -- 1 root 4617 newman. config