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Command cat

The cat command belongs to file management, used to connect files and print them to the standard output device. cat is often used to display the contents of a file. However, when the file is large, the text quickly flashes on the screen causing scrolling. At this time, it's often difficult to see the displayed content. To control scrolling, you can press Ctrl+S to stop scrolling and Ctrl+Q to resume scrolling. Additionally, you can use commands like more to read and display files page by page.

Syntax

cat [-AbeEnstTuv] [--help] [--version] fileName

Parameters

  • -n or --number: Number all output lines, starting from 1.
  • -b or --number-nonblank: Similar to -n, but do not number the blank lines.
  • -s or --squeeze-blank: Replace multiple consecutive blank lines with a single blank line.
  • -v or --show-nonprinting: Display control characters like ^ and M-, except for LFD and TAB.
  • -E or --show-ends: Display a $ at the end of each line.
  • -T or --show-tabs: Display TAB characters as ^I.
  • -A or --show-all: Equivalent to -vET.
  • -e: Equivalent to -vE option.
  • -t: Equivalent to -vT option.

Examples

Use the cat command to create a file, enter the file information, and then press Ctrl+D to output the EOF symbol and end the input.

cat > file.txt

Display the contents of the file.txt file.

cat file.txt

Simultaneously display the contents of the file.txt and file2.txt files.

cat file.txt file2.txt

Append the content of the file.txt file with line numbers to the file2.txt file.

cat -n file.txt >> file2.txt

Empty the file2.txt file. /dev/null is called a null device and is a special device file that discards all data written to it but reports the write operation as successful. Reading from it will immediately return an EOF.

cat /dev/null > file2.txt

Merge the content of the file.txt and file2.txt files and output them to file3.txt.

cat file.txt file2.txt > file3.txt

Daily Question

https://github.com/WindrunnerMax/EveryDay

References

https://man.linuxde.net/cat
https://www.runoob.com/linux/linux-comm-cat.html
https://www.cnblogs.com/zhangchenliang/p/7717602.html