Shell Script Question Read Parameters from a textfile

supermonkey

Hi all,

The script below is intended to help in exporting a wordpress website from a staging server to a domain.

It accepts 2 inputs an old domain and a new domain. These are put in manually at the start of the export process.

I would like to read in a list of old domains and new domains in the following format

fish.staging.ie:ilovefish.ie
cows.staging.ie:thecowssite.com
love.staging.ie:whatislove.net

and have the process run automatically.

This is the process as it stands I prompt myself for both values.

#!/bin/bash
#Script to alter text in database in order to prepare a 
#wordpress website for export
read -p "Enter the old  domain name :   " OLD_DOMAIN
read -p "Enter the new domain name :   " NEW_DOMAIN

PATH_TO="/supermonkey/newsites/"

/usr/bin/mysqldump  -f -u "DBUSER""$OLD_DOMAIN" -p[PASSWORD] "$OLD_DOMAIN" 
>""$PATH_TO"/"$NEW_DOMAIN"/"$NEW_DOMAIN".SQL"
SQL_FILE=""$PATH_TO"/"$NEW_DOMAIN"/"$NEW_DOMAIN".SQL"


sed "s|$OLD_DOMAIN|$NEW_DOMAIN|g" "$PATH_TO"/"$OLD_DOMAIN"/"$OLD_DOMAIN".SQL> "$PATH_TO"/"$OLD_DOMAIN"/"$NEW_DOMAIN""01"".SQL"

I tried this before and it worked but only if the file only contained 1 pair of values. Otherwise the sed happened at what looked like random.

#!/bin/bash

#Script to read a list of files and convert databases
while IFS=: read OLD_DOMAIN NEW_DOMAIN
do  


done < /home/supermonkey/allsites/supmdomainlist.txt

Skrynesaver

~/src $ cat test.txt
one:two
three:four
~/src $ for i in $(cat test.txt);do first=$(echo $i|cut -d\: -f1);second=$(echo $i |cut -d\: -f2 );echo "First is $first and Second is $second";done;
First is one and Second is two
First is three and Second is four

supermonkey

Thanks Skrynesaver,
The example works.
Now I have to understand it and relate it to my own script.

for i in $(cat test.txt);
do first=$(echo $i|cut -d\: -f1);
second=$(echo $i |cut -d\: -f2 );
echo "First is $first and Second is $second";
done;

for i in $(cat test.txt);

Sets up a for loop.
How does UNIX know that the counter and the line number are the same?
Is any file that we cat assumed to contain meaningful records?

do first=$(echo $i|cut -d\: -f1);
second=$(echo $i |cut -d\: -f2 );

echo $i gets the counter and therefore the line number
cut -d\: specifies that the field delimiter is :
first is assigned to field 1 -f1
second is assigned to field 2 -f2

Skrynesaver

supermonkey wrote: »

Thanks Skrynesaver,
The example works.
Now I have to understand it and relate it to my own script.

The notion is to treat each line as a record $i then use cut to isolate specific fields using a field separator ":"
The cut command takes a delimiter and a field to return.
This was a quick hack, hope it can be integrated

supermonkey

Skrynesaver wrote: »

The notion is to treat each line as a record $i then use cut to isolate specific fields using a field separator ":"
The cut command takes a delimiter and a field to return.
This was a quick hack, hope it can be integrated

Is each line being a record implicit in when you cat a file? I really have to get a handle on piping!!!:p

Skrynesaver

supermonkey wrote: »

Is each line being a record implicit in when you cat a file? I really have to get a handle on piping!!!:p

There is a shell variable $IFS which is used by the for loop to determine where each record ends.

It's not a c style for loop, it assigns the value of the current record to $i in the loop,

supermonkey

Skrynesaver wrote: »

There is a shell variable $IFS which is used by the for loop to determine where each record ends.

And that variable is newline by default? Meaning that if I use newline I don't specify $IFS? I really got this wrong. Thought $IFS was the field delimiter no wonder it didn't work!

Skrynesaver

supermonkey wrote: »

And that variable is newline by default? Meaning that if I use newline I don't specify $IFS? I really got this wrong. Thought $IFS was the field delimiter no wonder it didn't work!

IFS (Internal Field Seperator) is the field delimiter, but we're treating the field the for loop isolates as a record.