Linux cat Command

The cat (short for "concatenate") command is used to concatenate files and print them to the standard output device.

All users

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

-n or --number: Number all output lines starting from 1.

-b or --number-nonblank: Similar to -n, but does not number blank lines.

-s or --squeeze-blank: Substitutes multiple consecutive blank lines with a single blank line.

-v or --show-nonprinting: Uses ^ and M- notation, except for LFD and TAB.

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

-T or --show-tabs: Displays TAB characters as ^I.

-A, --show-all: Equivalent to -vET.

-e: Equivalent to "-vE" option;

-t: Equivalent to "-vT" option;

Add line numbers to the content of textfile1 and output it to textfile2:

cat -n textfile1 > textfile2

Add line numbers (excluding blank lines) to the content of textfile1 and textfile2, then append it to textfile3:

cat -b textfile1 textfile2 >> textfile3

Empty the contents of the /etc/test.txt file:

cat /dev/null > /etc/test.txt

The cat command can also be used to create image files. For example, to create a floppy disk image file, insert the floppy disk and enter:

cat /dev/fd0 > OUTFILE

Conversely, to write an image file to a floppy disk, enter:

cat IMG_FILE > /dev/fd0

Note:

1. OUTFILE refers to the output image file name.
1. IMG_FILE refers to the image file.
1. When writing back to the device from the image file, the device capacity must be equivalent.
1. Typically used to create bootable disks.