Why does recursive mode on chmod do everything but recursion?

Question

chmod -R 775 *.cgi only changes permissions on the files in the current directory, the files in the subdirectory don't get modified at all. This is the exact same functionality as simply doing chmod 775 *.cgi. I have seen people use solutions such as with find and whatnot. Ok great, but why does -R mode even exist if it doesn't even accomplish anything?

Answer 1

Probably because you have no directories named *.cgi. Quoth the manual:

-R Recursively change file mode bits. For each file operand that names a directory, chmod shall change the file mode bits of the directory and all files in the file hierarchy below it.

For example:

$ ls -R
.:
a  a.c  b.c  c.c

./a:
a.c  b.c  sub

./a/sub:
a.c  b.c  
$ chmod -R 444 *.c
$ ls -l
drwxr-xr-x 3 msw msw 4096 2010-08-12 18:07 a
-r--r--r-- 1 msw msw    0 2010-08-12 18:07 a.c
-r--r--r-- 1 msw msw    0 2010-08-12 18:07 b.c
-r--r--r-- 1 msw msw    0 2010-08-12 18:07 c.c
$ : directory a not affected
$ chmod -R u-w a    
$ ls -l a
-r-xr-xr-x 1 msw msw    0 2010-08-12 18:07 a.c
-r-xr-xr-x 1 msw msw    0 2010-08-12 18:07 b.c
dr-xr-xr-x 3 msw msw 4096 2010-08-12 18:07 sub
$ ls -l a/sub
-r-xr-xr-x 1 msw msw    0 2010-08-12 18:07 a.c
-r-xr-xr-x 1 msw msw    0 2010-08-12 18:07 b.c
$ : got em

Answer 2

-R tells chmod to recurse into any directories that are given as arguments.

If you say chmod -R 775 *.cgi, the shell will expand *.cgi into a list of files which match that pattern, and pass that as the list of arguments - so chmod isn't being asked to look into any other directories.

(It will recurse into any directory which matches *.cgi...)

Answer 3

To accomplish what you want try

find . -name '*.cgi' -print0 | xargs -0 chmod 755

Here find generates a list of all the file with a .cgi ending from the current directory downward, and passes that list to xargs which applies chmod to each one.

Answer 4

*.cgi is expanded by your shell to a list of all the file names in the current directory ending in .cgi. Then the shell calls chmod with this list of filenames.

chmod looks at all those file names it got from the shell, changes there modes and would recurse if some of them were directories. But probably none of them are, so there is nothing to recurse.

To find all cgi files in the current directory and its subdirectories, and run chmod on them, you could do:

find . -name '*.cgi' -print0 | xargs -0 chmod 775

Answer 5

* is a shell builtin, while -R is a command line option. So chmod will never get * as an argument.

Put the case that foo0.cgi and foo1.cgi are the contents of the directory. If you type chmod -R o+r *.cgi then chmod will get the '-R', 'o+r', 'foo0.cgi' and 'foo1.cgi' as arguments.

What you want to do can be accomplished easily:

find . -iname '*.cgi' | xargs chmod 755