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cp

summary

    This subchapter looks at cp, a UNIX (and Linux) command.

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cp

    This subchapter looks at cp, a UNIX (and Linux) command.

    cp is used to copy a file.

    cp was part of the original 1969 version of UNICS (the original name for UNIX).

copy a file

    Use the cp command to make a copy of a file. This example assumes you created the names file in the quick tour subchapter.

    $ cp names saved_names
    $

    Notice that there is no confirmation of the file copy being made.

    This silent behavior is typical of any UNIX shell. The shell will typically report errors, but remain silent on success. While disconcerting to those new to UNIX or Linux, you become accustomed to it. The original purpose was to save paper. When UNIX was first created, the terminals were mostly teletype machines and all output was printed to a roll of paper. It made sense to conserve on paper use to keep costs down.

    You can use the ls command to confirm that the copy really was made. You won’t be using up any paper.

    $ ls
    Desktop          Movies        Send registration
    Documents        Music         Sites
    Downloads        Pictures      names
    Library          Public        saved_names
    $

    cp makes an exact copy of a file.

common errors

    Common errors:

• the source is a directory
• the source does not exist
• attempt to copy a file to itself

overwriting files

    The plain cp command will simply replace any existing file with a matching name. No warning.

    $ cp names saved_names
    $

    In the above example, if the file save_names already existed, it will be replaced with a copy of names.

interactive confirmation

    You can type cp -i to get an interactive confirmation before replacing a file. Enter n or just the RETURN key to stop the copy and prevent an overwrite. Enter y to go ahead with the copy and replace the old file.

    $ cp -i names saved_names
    overwrite saved_names? (y/n [n]) n
    not overwritten
    $

force overwrites

    Use the -f option to force the copy to overwrite any file with a matching name. This is the same as the default action of the cp command.

    $ cp -f names saved_names

copy to a directory

    To copy a file to a different directory, name the directory with a leading slash (/) as the destination:

    $ cp sourcefilename directory/

    Try this example:

    $ cp names testdir/
    $ ls testdir
    names
    $

    A copy of the file will be stored in the specified directory with the original name. You can add a new file name after the directory if you want to change the name of the copy at the same time you create it in the specified directory.

    $ cp sourcefilename /directory/newname

    Try this example:

    $ cp names testdir/newnames
    $ ls testdir
    names           newnames
    $

copying an entire directory

    To copy an entire source directory to a different directory, name each directory:

    $ cp sourcedirectory destinationdirectory/

    This does not work on all systems without using the -r or -R switch (see next item).

copying an entire directory and subdirectories

    If you want to copy a directory and all of its subdirectories (the directory subtree), then use the recursive switch. The recursive switch will be either -r or -R. Check the man page for your system.

    $ cp -r sourcedirectory destinationdirectory/

    Mac OS X supports both the -r and the -R switches for compatibility with legacy scripts, but on Mac OS X the -r option will not correctly copy special files, symbolic links, or fifos, while the -R option will copy them correctly.

    Try this example:

    $ cp -r testdir newdir/
    $ ls newdir
    names           newnames
    $

copying multiple items to a directory

    You can create a list of sources (both files and directories) that are all put into a single destination directory. The last item listed must be a directory and is the destination. You can optionally use the -r or -R flag (which ever is appropriate for your system) to recursively copy source directories with all of their subdirectories. SOme systems may require the -r or -R switch if you include directories as well as files int he source list.

    $ cp sourcedirectory1/ sourcedirectory2/sourcefile destinationdirectory/

common error

    A common error is that the destination folder already exists.

PC-DOS equivalent

    cp -i is the UNIX equivalent of the MS-DOS or PC-DOS command COPY. You can add the PC-DOS equivalent to your shell session with the alias command. To make the change permanent, add the following line to the .bashrc file in your home directory. Note that this version adds interactive questioning before replacing a file, in a manner similar to PC-DOS. Note also that if you add this PC-DOS/MS-DOS equivalent, only add the all upper case version, because the lower case type is an important UNIX command that you will also need.

    $ alias COPY="cp -i"

other

    On November 8, 2010, Ramesh Natarajan named this the number 28 most frequently used UNIX/Linux command at this web page 50 Most Frequently Used UNIX / Linux Commands (With Examples).

    In June 2009, Ken Milberg named this command as one of the Top 50 universal UNIX commands at this web page Top 50 Universal INIX commands. Note that this web page requires agreeing to be spammed before you can read it.

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