command not found when using sudo

Check for secure_path on sudo

[root@host ~]# sudo -V | grep 'Value to override'
Value to override user's $PATH with: /sbin:/bin:/usr/sbin:/usr/bin

If $PATH is being overridden use visudo and edit /etc/sudoers

Defaults    secure_path = /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin

Permission denied

In order to run a script the file must have an executable permission bit set.

In order to fully understand Linux file permissions you can study the documentation for the chmod command. chmod, an abbreviation of change mode, is the command that is used to change the permission settings of a file.

To read the chmod documentation for your local system , run man chmod or info chmod from the command line. Once read and understood you should be able to understand the output of running ...

ls -l foo.sh

... which will list the READ, WRITE and EXECUTE permissions for the file owner, the group owner and everyone else who is not the file owner or a member of the group to which the file belongs (that last permission group is sometimes referred to as "world" or "other")

Here's a summary of how to troubleshoot the Permission Denied error in your case.

$ ls -l foo.sh                    # Check file permissions of foo
-rw-r--r-- 1 rkielty users 0 2012-10-21 14:47 foo.sh 
    ^^^ 
 ^^^ | ^^^   ^^^^^^^ ^^^^^
  |  |  |       |       | 
Owner| World    |       |
     |          |    Name of
   Group        |     Group
             Name of 
              Owner 

Owner has read and write access rw but the - indicates that the executable permission is missing

The chmod command fixes that. (Group and other only have read permission set on the file, they cannot write to it or execute it)

$ chmod +x foo.sh               # The owner can set the executable permission on foo.sh
$ ls -l foo.sh                  # Now we see an x after the rw 
-rwxr-xr-x 1 rkielty users 0 2012-10-21 14:47 foo.sh
   ^  ^  ^

foo.sh is now executable as far as Linux is concerned.

Using sudo results in Command not found

When you run a command using sudo you are effectively running it as the superuser or root.

The reason that the root user is not finding your command is likely that the PATH environment variable for root does not include the directory where foo.sh is located. Hence the command is not found.

The PATH environment variable contains a list of directories which are searched for commands. Each user sets their own PATH variable according to their needs. To see what it is set to run

env | grep ^PATH

Here's some sample output of running the above env command first as an ordinary user and then as the root user using sudo

rkielty@rkielty-laptop:~$ env | grep ^PATH
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games

rkielty@rkielty-laptop:~$ sudo env | grep ^PATH
[sudo] password for rkielty: 
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/X11R6/bin

Note that, although similar, in this case the directories contained in the PATH the non-privileged user (rkielty) and the super user are not the same.

The directory where foo.sh resides is not present in the PATH variable of the root user, hence the command not found error.

The other solutions I've seen here so far are based on some system definitions, but it's in fact possible to have sudo use the current PATH (with the env command) and/or the rest of the environment (with the -E option) just by invoking it right:

sudo -E env "PATH=$PATH" <command> [arguments]

In fact, one can make an alias out of it:

alias mysudo='sudo -E env "PATH=$PATH"'

(It's also possible to name the alias itself sudo, replacing the original sudo.)