Linux one command per day: Cat

Linux Cat Command command: Cat

The cat command is used to connect files and print to standard output devices.

Use permissions

All Users

Syntax format

Cat[-ABEENSTTUV] [--help] [--Version] Filename[[email protected]]#Cat--Helpusage:Cat[OPTION] ... [FILE] ... Concatenate FILE (s), or standard input, to standard output.-A,--show-all equivalent to-VET-B,--number-nonblank number nonempty output lines, overrides-N-e equivalent to-VE-E,--show-ends display $ at end of each line-N,--Number number all output lines-S,--squeeze-blank suppress repeated empty output lines-T equivalent to-VT-T,--show-tabs display TAB characters as ^I-u (ignored)-V,--show-nonprinting use ^ and m-notation, except forLFD and TAB--Help display this help and exit--version output version information and Exitwith no file, or when file is-, read standard input. Examples:CatF-g Output F's contents, then standard input, then G's contents.CatCopy standard input to standard output.

Parameter description:

- N or--number: Numbers The number of rows for all outputs starting from 1.

- B or--number-nonblank: similar to-n, except that blank lines are not numbered.

- s or--squeeze-blank: a blank line that is substituted for a row when it encounters a blank line that has more than two consecutive lines.

- V or--show-nonprinting: Use the ^ and m symbols, except for LFD and TAB.

- E or--show-ends : Displays $ at the end of each line.

- T or--show-tabs: Displays the TAB character as ^i.

- e : equivalent to-ve.

-A,--show-all: equivalent to-vet.

- E: equivalent to "-ve" option;

- T: equivalent to the "-vt" option;

Instance

Add the Textfile1 document content to the line number and enter Testfile2 in this document:

cat testfile1 > Testfile2

Append the contents of the Testfile1 and testfile2 documents to the TESTFILE3 document after adding line numbers (blank lines):

Cat -B testfile1 testfile2 >> testfile3

Empty the contents of the/etc/test document:

cat /dev/null > Testfile

Cat can also be used to make image files. For example, to make a floppy disk image file, put the floppy disk and enter:

cat /dev/fd0 > OUTFILE

Conversely, if you want to write the image file to a floppy disk, enter:

Cat Img_file >/dev/fd0

Note :

• 1. OUTFILE refers to the image file name of the output.

• 2. Img_file refers to the image file.

• 3. If you write back to device from the image file, the device capacity needs to be equivalent.

• 4. Usually make the boot magnetic chip.

• 5. Usually/dev/null as a "black hole". It is very equivalent to a write-only file. All content written to it will be lost forever. While trying to read from it, nothing can be read. However,/dev/null is very useful for command lines and scripts.

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It is never too late to learn. --high-base

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Linux one command per day: Cat