Bash: Repeat commands until a condition is matched

iniuria · 03-08-2011, 12:01 PM

Hi everybody, i need to modify some scripts to repeat the commands in them until a variable returns a proper value. I need it to add some redundancy to some scripts i use to upload files to a remote server.

This is an example of a portion of those scripts:

Code:

################## site UPLOAD ##################

site_login=$(curl -c $site_cookie -L -F user=$site_user -F pass=$site_password -F submit=Login http://site.com/login.html)
site_page=$(curl -b $site_cookie -c $site_cookie http://site.com)

site_action=$(echo "$site_page" | grep "site.com/upload.php" | cut -f2 -d"\"")
site_progress_key=$(echo "$site_page" | grep "progress_key" | grep -o "value=\"[0-9a-zA-Z]*\"" | cut -f2 -d"\"")
site_usergroup_key=$(echo "$site_page" | grep "usergroup_key" | grep -o "value=\"[0-9a-zA-Z]*\"" | cut -f2 -d"\"")
site_UPLOAD_IDENTIFIER=$(echo "$site_page" | grep "UPLOAD_IDENTIFIER" | grep -o "value=\"[0-9a-zA-Z]*\"" | cut -f2 -d"\"")

post=$(echo "-F APC_UPLOAD_PROGRESS=$site_progress_key -F APC_UPLOAD_USERGROUP=$site_usergroup_key -F UPLOAD_IDENTIFIER=$site_UPLOAD_IDENTIFIER")


results_site=$(curl -L -b $site_cookie $post $site_action -F file[]='' -F file[1]=@$scenes_directory/$f -F submit=Upload)

site_link=$(echo "$results_site" | grep -o "http://site.com/files\/[a-zA-Z./0-9_-]*" | sed q)

Now i need to verify if the variable site_link has a proper value (it should match the regex http://site.com/files\/[a-zA-Z./0-9_-]*), and if it hasnt, reapeat the previous commands to retry the upload UNTIL a proper link is set.

Any idea on how to do it?

I guess a WHILE is needed, but i never used it, so i'm not sure on where to place it or how to write it.

Thanks.

z1p · 03-08-2011, 04:55 PM

An until seems to fit better into the logic of what your script is doing.

The general format of an until loop is:

Code:

 until test-commands; do consequent-commands; done

See http://www.gnu.org/software/bash/man...ing-Constructs

In your case I'd say you'll want to modify your script along the lines of:

Code:

site_link=""

until [[ "$site_link" != "" ]]
do
   results_site=$(curl -L -b $site_cookie $post $site_action -F file[]='' -F file[1]=@$scenes_directory/$f -F submit=Upload)
   site_link=$(echo "$results_site" | grep -o "http://site.com/files\/[a-zA-Z./0-9_-]*" | sed q)
done

You'll most likely want to wait some between your posts so you don't flood the server and possibly also include some other exit conditions like max number of tries.

grail · 03-08-2011, 06:55 PM

OT - I was just wondering what value the 'sed q' gives at the end of site_link command substitution?

Reuti · 03-09-2011, 05:51 AM

Quote:

Originally Posted by grail

OT - I was just wondering what value the 'sed q' gives at the end of site_link command substitution?

AFAICS it should be the first line of the stream, like head -1.

iniuria · 03-09-2011, 09:54 AM

Thanks z1p, yours is a good solution. Everything changes if i output the result_site to a txt file, use a WAIT, and then read the site_link from that TXT, i willpost some exampla later.

@ grail and reuti

The sed -q was used because the regex returned two or more lines, while i just needed one of them.