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This documentation reflects EDirect version 10.9, released on 2/1/2019.

We strive to keep this documentation up-to-date with the latest release. If you are looking for documentation on a more recent version of EDirect, or to find out more about new EDirect releases, please see the Release Notes of NCBI's EDirect documentation.

The cat command, short for “concatenate”, is a Unix command with several functions. Among other things, cat can open one or more files and output their contents to “standard output” (i.e. the terminal screen). To see a full list of arguments, options, and features of cat, see the cat documentation page, or type

man cat

into your terminal to see the manual page for cat.


One or more files.


The contents of the input files to “standard output” (i.e. the terminal screen)


Opens the file “file1.txt” and displays the contents in the terminal:

cat file1.txt

Opens the files “file1.txt” and “file2.txt” and displays them, one after the other, in the terminal:

cat file1.txt file2.txt