Table of contents
cut command
Function
The cut command cuts bytes, characters, and fields from each line of a file and writes them to standard output.
If you do not specify the File parameter, the cut command reads standard input. One of the -b, -c, or -f flags must be specified.
grammar
cut [options] filename
parameter
| parameter | illustrate |
|---|---|
| -b | Split in bytes. These byte positions ignore multibyte character boundaries unless the -n flag is also specified. |
| -c | Split by character. |
| -d | Custom delimiter, default is tab. |
| -f | Used with -d, specifies which region to display. |
| -n | Unsplit multibyte characters. Only used with the -b flag. If the last byte of a character falls within the range indicated by the List parameter of the -b flag, the character will be written; otherwise, the character will be excluded |
example
test text
The spaces in the student table text here must use tabs, and the number of tabs must be the same .
Extract names of all rows
Order:cut -f 2 student.txt
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Extract names and ratings for all rows
Order:cut -f 2,4 student.txt
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split text
According to: split, output the first and third columns
Command:cut -d ":" -f 1,3 /etc/passwd
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Extract the username of the user in /etc/passwd
Order:cut /etc/passwd | grep /bin/bash | cut -d ":" -f 1
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Limitations of the cut command
Cannot be used for space separation and the number of tabs must be the same or,. |: Equal symbol
printf command
Function
printf uses quoted text or space-separated parameters, and format strings can be used in printf outside, and the width of the string, left and right alignment, etc. can also be specified. The default printf does not automatically add newlines like echo, we can manually add \n.
grammar
printf "output type output format" output content
parameter
output type
| Format | illustrate |
|---|---|
| %ns | output string. n is a number indicating how many characters to output |
| %in | Output integers. n is a number to indicate how many numbers to output |
| %m.nf | Output floating point number. m and n are numbers that refer to the number of integer and decimal digits of the output. For example, %8.2f means to output a total of 8 digits, including 2 decimals and 6 integers |
output format
| Format | illustrate |
|---|---|
| \a | output warning sound |
| \b | Output the backspace key, which is Backspace |
| \f | clear screen |
| \n | newline |
| \r | Enter, that is, Enter |
| \t | Horizontal output backspace key, that is, tab |
| \in | Vertical output backspace key, that is, tab |
example
Notice:Format characters are enclosed in quotation marks
output in string format
Order:printf %s 1 2 3 4 5 6
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Control column count output
Order:printf '%s %s %s\n' 1 2 3 4 5 6
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Do not adjust output file content
The printf command can be used with cat, similar to chain programming.
Order:printf '%s' $(cat ./test/student.txt)
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Adjust output file content
Order:printf '%s\t %s\t %s\t %s\n' $(cat ./test/student.txt)
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