Execute an array of string describing shell command

Question

I'm struggling to execute a set of command lines stored as strings in an array. My code looks like this :

arr=( "sudo apt-get update" "sudo apt-get install xxx" )
...
arr=( ${arr[@]} "ln -s /path1 /path2" )
etc...

# Then I loop on the array of command 
for (( i = 0 ; i < ${#arr[@]} ; i++ ))
do
     eval ${arr[$i]}
done

When it loops over the array, the array is larger than the number of command stored into it. As if the blank spaces in my strings split the array in more elements A typical ouput is such like

usage: sudo -h | -K | -k | -L | -V

That means only 'sudo' is taken from within the string and I don't understand why!

Thanks

Answer 1

Use ${#arr[@]} to get the number of items in the array (${arr[@]} gives the word count). Using either eval or back-ticks (`) to execute the command works:

[ 15:20 jon@host ~ ]$ cat run_yum_test.sh
#!/bin/bash

declare -a arr=("sudo yum search zsh" "sudo yum list zsh")

for (( i = 0; i < ${#arr[@]} ; i++ )); do
    printf "\n**** Running: ${arr[$i]} *****\n\n"

    # Run each command in array 
    eval "${arr[$i]}"

    ### using back-ticks works also
    #RESULT=`${arr[$i]}`
    ### Check if the command gave any output
    #if [ -n "$RESULT" ]; then
    #    echo "$RESULT"
    #fi
done

[ 15:20 jon@host ~ ]$ ./run_yum_test.sh

**** Running: sudo yum search zsh *****

[sudo] password for jon:
Loaded plugins: presto, refresh-packagekit
=========================================================================== Matched: zsh ===========================================================================
zsh-html.i686 : Zsh shell manual in html format
autojump-zsh.noarch : Autojump for zsh
fatrat-czshare.i686 : FatRat plugin enabling CZShare.com downloads and uploads
gromacs-zsh.noarch : GROMACS zsh support
python-twisted-core-zsh.i686 : Tab completion for Zsh and Twisted Core
zsh.i686 : A powerful interactive shell
environment-modules.i686 : Provides dynamic modification of a user's environment
plowshare.noarch : CLI downloader/uploader for some of the most popular file-sharing websites

**** Running: sudo yum list zsh *****

Loaded plugins: presto, refresh-packagekit
Available Packages
zsh.i686                                                                    4.3.10-6.fc13                                                                    updates

---

Edit (to answer your comment):

To "extend" the array, put the original array (${arr[@]}) in quotes, like so:

arr=("sudo yum list zsh" "sudo yum search zsh")
arr=("${arr[@]}" "echo 'TEST'")

Here it is in action:

[ 16:06 jon@host ~ ]$ cat run_yum_test.sh
#!/bin/bash

arr=("sudo yum list zsh" "sudo yum search zsh")
arr=("${arr[@]}" "echo 'TEST'")

for (( i = 0; i < ${#arr[@]} ; i++ )); do
    printf "\n**** Running: ${arr[$i]} *****\n\n"
    eval "${arr[$i]}"
done


[ 16:06 jon@host ~ ]$ ./run_yum_test.sh

**** Running: sudo yum list zsh *****
[sudo] password for jon:
Loaded plugins: presto, refresh-packagekit
Available Packages
zsh.i686                                                                    4.3.10-6.fc13                                                                    updates

**** Running: sudo yum search zsh *****

Loaded plugins: presto, refresh-packagekit
=========================================================================== Matched: zsh ===========================================================================
zsh-html.i686 : Zsh shell manual in html format
autojump-zsh.noarch : Autojump for zsh
fatrat-czshare.i686 : FatRat plugin enabling CZShare.com downloads and uploads
gromacs-zsh.noarch : GROMACS zsh support
python-twisted-core-zsh.i686 : Tab completion for Zsh and Twisted Core
zsh.i686 : A powerful interactive shell
environment-modules.i686 : Provides dynamic modification of a user's environment
plowshare.noarch : CLI downloader/uploader for some of the most popular file-sharing websites

**** Running: echo 'TEST' *****

TEST