Compare files using Unix scripting

Shell Programming and Scripting
1

I have a file containing the below data obtained after running a diff command

> abc 10
< abc 15
> xyz 02
<xyz 05

.....

Does anyone know how i can obtain output like :

previous value of abc is 10 and present value is 15

similarly for all the comparisons in the text file

2

Could this help you ?

diff -b --side-by-side --suppress-common-lines file1 file2
3

The o/p printed is the result of the diff operation .

i need to print old values and new values of abc , xyz etc using that result . how do i do that

4

If your diff output is as simple as you posted, then try this:

awk '
    { gsub( "^.", "& " ); }   # needed if leading "<" isnt always separated by whitespace from rest of line
    /^</ {
        if( old[$2] )
            printf( "%s  old=\"%s\"  new=\"%s\"\n", $2, old[$2], $3 );
        else
            new[$2] = $3;
    }
    /^>/ {
        if( new[$2] )
            printf( "%s  old=\"%s\"  new=\"%s\"\n", $2, $3, new[$2] );
        else
            old[$2] = $3;
    }
'  input >output

Output should be something like:

abc  old="10"  new="15"
xyz  old="02"  new="05"
5

What if i'm readin the diff ouput from a file ?

6

Replace 'input' on the awk command with your file name. If the file is in diff.out, then

awk '

# lines of awk programme
' diff.out
7

I would want to redirect this output to file also .

printf( "%s  old=\"%s\"  new=\"%s\"\n", $2, $3, new[$2] )

Currently i'm getting an error like :

awk:cmd line:11 (filename=input.txt FNR=4) fatal:division by zero

attempted when i'm trying

printf( "%s  old=\"%s\"  new=\"%s\"\n", $2, $3, new[$2] ) > output.txt

in the snippet of code given

---------- Post updated 2012-09-25 at 01:56 AM ---------- Previous update was 2012-09-24 at 01:22 PM ----------

Any solutions ??

8

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9

If this is truly in awk, you need > "filename.txt" with the filename in quotes.

But you haven't posted your entire code, so I have no idea why it's complaining about division by zero.

10

Thanks a lot !!! It worked .. Btw could you explain why i need to put in Quotes ???

11

Because if you don't, it will take it to be a variable name. awk's not shell. :slight_smile: