cat is a standard Unix utility used for concatenating files or printing specific file on the standard output.
cat is a standard Unix utility used for concatenating files or printing specific file on the standard output.
The cat program is given files in a sequence as arguments, it will output their contents to the standard output in the same sequence.
Examples
Printing the contents of a file on the standard output.
cat -n file.txt # n stands for line-numbers
Concatenating two files into third file:
cat file1.txt file2.txt > output_file
The purpose of cat is to concatenate (or catenate) files. If it is only one file, concatenating it with nothing at all is a waste of time, and costs you a process. This is also referred to as "cat abuse".
Nevertheless the following usage is common:
cat filename | command arg1 arg2 argn
cat -- "$file" | grep -- "$pattern"
cat -- "$file" | less
can instead be written as:
grep -- "$pattern" "$file"
less "$file"
