bash variable referencing question.

zcarlile · 01-10-2014, 02:43 PM

Hello,

I am new into the bash programming. I am working on a script to use to verify uniformity on large files of sql statements. below is my current code.

Code:

#!/bin/bash

echo "What SQL do ya want to check???"
read fname

##The script is suppose to check your inpute fname to make sure its a regular file. if it is then its suppose to break down the individual parts and echo it out.

if [ -f $fname ]
then
        for i in {1..26}; 
        do echo "-------------------- checking field $i";
        cat $fname | awk -v v="$fname" '{print $v}' | sort | uniq | head; done
 else 
        echo "this is not a file"
 
fi

My question is this: fname refers to the file name input, How would I write the loop? I need to set a varuable for the command but in the loop its going to be refering to fname.

grail · 01-10-2014, 11:07 PM

Firstly, quotes, quotes and more quotes. Variables without quotes in bash can cause unpredictable results.

You may need to explain further what you need as the cat, awk, sort, uniq and head output is not clear (I would add that awk can probably do all of those for you)

As for reading a file, use a while, read loop:

Code:

while read var
do
   <your stuff here>
done<"$fname"

Here 'var' will store each line read from the file for you to work on.

If this is not what you require, please explain further?

zcarlile · 01-14-2014, 09:59 AM

Basically at my job I often deal with 1k+ lines of duplicate SQL statements. My objective is to have the awk break it down so that I can check to make sure that my formating is correct. The following command line will do this.

Quote:

for i in {1..26}; do echo "-------------------- checking field $i"; cat /blah/blah/blah | awk -v v="$i" '{print $v}' | sort | uniq | head; done

will do what I need but I dont want to type the command line every time I need to run this.

My question is this.
I want my syntax as follows:
./script_name file_to_be_checked_name
displays the output from the above command line.

My problem is I have no formal training with bash, and dable in very little.
I know that the loop for in `blah` is naming blah as variable i which is fine, but how to write the code to do variable i on variable fname

grail · 01-14-2014, 11:12 AM

Do not use for to read a file. (http://mywiki.wooledge.org/DontReadLinesWithFor)

Simply alter your code to test for an argument (the filename) and then assign using its position on the line ($1 being the first argument) to fname.

I would also maintain that the conglomeration of commands is not required but we would need to see the format of the file and what you are trying to achieve to help further.