Concatenate and print (display) the content of files. Concatenate FILE(s), or standard input, to standard output.
Syntax
cat [Options] [File]...
Options
-A, --show-all equivalent to -vET
-b, --number-nonblank number nonblank output lines
-e equivalent to -vE
-E, --show-ends display $ at end of each line
-n, --number number all output lines
-s, --squeeze-blank never more than one single blank line
-t equivalent to -vT
-T, --show-tabs display TAB characters as ^I
-u (ignored)
-v, --show-nonprinting use ^ and M- notation, except for LFD and TAB
--help display this help and exit
--version output version information and exit
With no FILE, or when FILE is -, read standard input.
When given a single FILE, cat will pass the file unchanged to STDOUT (by default the display).
The cat utility does not buffer its output when writing to a pipe.
The cat command can be piped into grep to find specific words in the file:
cat file.txt | grep keyword output.txt
However all modern versions of grep have this built-in. Running a single command/process is more efficient, and so with large files will be noticably faster:
grep keyword file.txt output.txt
grep can also display an entire file, (like cat), by using the grep keyword "." which will match lines with at least 1 character. Alternatively the grep keyword "^" will match the beginning of every line including blank lines.
When grep is used to display multiple files, it will prepend each line of output with the filename:
$ grep . *.txt
Display a file:
$ cat myfile.txt
Display all .txt files:
$ cat *.txt
Concatenate two files:
$ cat File1.txt File2.txt > union.txt
If you need to combine two files but also eliminate duplicates, this can be done with sort unique:
$ sort -u File1.txt File2.txt > unique_union.txt
Put the contents of a file into a variable:
$ my_variable='cat File3.txt'
View CPU and memory information:
class="code">$ cat /proc/cpuinfo
$ cat /proc/meminfo
"To be nobody but yourself - in a world which is doing its best, night and day, to make you like everybody else - means to fight the hardest battle which any human being can fight, and never stop fighting” ~ E. E. Cummings
cp - Copy one or more files to another location.
mv - Move or rename files or directories.
pv - Monitor the progress of data through a pipe.
tac - Concatenate and write files in reverse.
hexdump - View binary file
Stupid Cat tricks - by Mike Chirico.
Equivalent Windows command: TYPE - Display the contents of a text file.