Text processing commands

I. # WC: print the number of newlines, words, and bytes in files

WC [Option] [file]

-L: Statistical line

-C: counts the number of bytes.

-W: Number of words

For example: A. count the number of users in the current system: WC-L/etc/passwd

B. Count the files in/bin: ls-L/bin | WC-l

C. count the number of files starting with P in the/etc directory: ls-D/etc/[PP] * | WC-l

2. # TR: Convert or delete characters in translate, and use pipelines |

For example, a, CAT/etc/issue | tr 'a-Z': converts letters in issue to uppercase letters.

B. Echo "Hello World" | tr 'abcdefg': Convert the abcdefg contained in Hello World

Convert to uppercase.

C. Echo "Hello World" | tr-D 'abcdefg': Delete the characters in "Hello World" that contain abcdefg.

D, head-7/etc/passwd | tail-1 | cut-D:-F1 | tr 'a-z'' A-Z ': retrieve the username in line 1 of the/etc/passwd file and convert it to uppercase characters

3. # Cut: Cut, separated and displayed based on the specified separator.

Echo "this is a new line." | cut-d'-F1

Cut-D:-F1/etc/passwd = CAT/etc/passwd | cut-D:-F1 show all user names

CAT/etc/passwd | cut-D:-F1, 7 show all users and their shells

Head-7/etc/passwd | tail-1 | cut-D:-F1, retrieve the username in row 7th of the/etc/passwd file

Iv. # sort: sort the output file content.

Sort [Option] File

-F: Case Insensitive characters.

-N: Compare the content by numerical value.

-T: Specifies the delimiter.

-K: Specifies the comparison field after segmentation

-U: duplicate rows (repeated rows are consecutive rows), only once.

For example:

A, sort/etc/fstab

B. CAT/etc/passwd | cut-D:-F3 | sort-N = cut-D:-F3/etc/passwd | sort-N sorts the IDs of all users.

C. Cut-D:-F7/etc/passwd | sort-u displays the shells of all users on the current system, and the shell in the cup is only displayed once.

V. # uniq: Remove duplicate rows (duplicate rows are continuous rows)

-C: count the number of duplicates in each row.

-D: only duplicate rows are displayed.

-U: displays only non-duplicate rows.

6. head and tail:

Extract the 7th rows of the/etc/passwd file: Head-7/etc/passwd | tail-1

Text processing commands