[X-Unix] Copying to multiple directories

[James Bucanek]

Harvey Riekoff wrote on Wednesday, March 10, 2004:

>I need to copy "fileA" to every users library folder in the Users 
>directory. The file resides at t he root level. The command that I have 
>been using is: cp -r fileA /Users/*/Library.  There is obviously 
>something that I am doing wrong because nothing is copying. Any help 
>would be appreciated.

Harvey,

The cp command's syntax is like this (use 'man ls' for the gory details):

    cp source_file target_file
    
- or -

    cp source_file [ source_file2 ...] target_directory

You can either copy one to another file, or you can copy one or more files to a single destination directory.

Remembering Shell Lessons 101, the wildcard globbing is done by the shell, not the tool.  When you use 'cp -r fileA /Users/*/Library' you aren't passing two arguments to the cp command.  You're passing 5: 'cp -r fileA /Users/A/Library /Users/B/Library /Users/C/Library /Users/D/Library'

The cp command gets this, looks at the last argument, sees that it's a directory, and switches into the second mode.  That is, it will attempt to copy the first four arguments (one file and three directories) into the last directory.

The -r option is useless.  There is no -r option for the cp command.

If you meant -R, then it would have copyied the entire Library folder of the first three users into the Library folder of the last user.  So you're lucky you used the wrong option!

The solution to your problem is run the cp command once for each destination user.  So you use the commands

    cp fileA /Users/A/Library
    cp filaA /Users/B/Library


    Brian Medley wrote on Wednesday, March 10, 2004:
    >$ ls -d /Users/*/Library | xargs -I % echo cp fileA %
    >cp fileA /Users/bpm/Library
    >cp fileA /Users/jasonp/Library
    >cp fileA /Users/jmh/Library

Brian's solution does this by using the ls command to list the directory names (echo would had do it too), then pipes this list to xargs.  xargs takes, as input, a list of filenames and executes a command with that list as the arguments.  It's primarily used to repeatedly executed commands with a list of files that too long to fit on one command line, but Brian has used it here with the -l (replace string) option to execute the command once for each input line (i.e. each directory name), replacing the '%' with the directory.  So, xargs takes the input (/Users/A/Library, /Users/B/Library, ...) and inserts that into the template ('echo cp fileA %'), and executes the command once for each.  This results in the output

    cp fileA /Users/bpm/Library
    cp fileA /Users/jasonp/Library
    ...

Brian obviously used the 'echo' command as a demonstration.  To do the actual copy, you'd omit that and let xargs execute the actual cp command.

A little less obscure solution is to write a loop, although you're more likely to see this solution in a script.

    (this example is in tcsh; bash has a different syntax)
    [whiterabbit:~] james% foreach i ( /Users/*/Library )
    foreach? echo cp fileA $i
    foreach? end
    cp fileA /Users/james/Library
    cp fileA /Users/testing/Library

The 'foreach' commands starts a loop that sets the 'i' variable to each argument in the list.  It then executes the subsequent list of commands using a different value for i until the list is exhausted.

And finally,

Harvey Riekoff wrote on Thursday, March 11, 2004:
>Also when I run the command "$ ls -d /Users/*/Library | xargs -I % echo  
>cp fileA %"  I get the following message "su: $: Command not found"

The '$' is not part of the command.  It's Brian's bash command prompt.  The command starts with 'ls ...'.

Hope that helps,

James

______________________________________________________
James Bucanek       <mailto:privatereply at gloaming.com>