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sed multiline substitution if a condition holds

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# 1  
Old 10-14-2011
sed multiline substitution if a condition holds
Hi.

I have the following text file (more precisely a Matlab script):

dummy1 = 5; varx = 'false'; dummy2 = 6;
% ... some general commands
% ...
dummy3 = 7; vary = 'option1'; dummy4 = 8;

Using sed I want to do the following action:

IF varx = 'false'
vary='NEW_VALUE_1'
ELSEIF varx='true'
vary='NEW_VALUE_2'
ELSE
nothing to do
END


varx/y might not be at the beginning/end of the line, as in the example above, and a generic number of spaces is before/after the '=' sign. An unknown number of lines is between the lines containing varx/y (see ...some general commands). Looking at the example above, sed should return the following:

dummy1 = 5; varx = 'false'; dummy2 = 6;
% ... some general commands
% ...
dummy3 = 7; vary = 'NEW_VALUE_1'; dummy4 = 8;


Thanks
Paolo
# 2  
Old 10-14-2011
I'm not sure I understand your conditions. Is the ELSE ever going to be executed except at the start of the file (i.e. before we encounter the first varx assignment)?

Put another way, what output would you expect from:
Code:
dummy3 = 7; vary = 'option1'; dummy4 = 8;
dummy1 = 5; varx = 'false'; dummy2 = 6;
dummy3 = 7; vary = 'option1'; dummy4 = 8;
dummy3 = 7; vary = 'option1'; dummy4 = 8;
dummy1 = 5; varx = 'true'; dummy2 = 6;
dummy3 = 7; vary = 'option1'; dummy4 = 8;

(with whatever in-between the varx/vary lines)


EDIT: A possible (and rather messy Smilie) awk solution:
Code:
#  cat xx.awk
BEGIN {
        FS=";";
        xval=-1;
        if (NEWVAL1=="") NEWVAL1="'optionA'";
        if (NEWVAL2=="") NEWVAL2="'optionB'";
}
$2 ~ /varx *= *'false'/ {
        xval=0;
        print;
}
$2 ~ /varx *= *'true'/ {
        xval=1;
        print;
}
$2 ~ /vary *= */ {
        if (xval==1) {
                printf ("%s; vary = %s", $1, NEWVAL2);
                x=3;
        }
        else if (xval==0) {
                printf ("%s; vary = %s", $1, NEWVAL1);
                x=3;
        }
        else {
                printf ("%s", $1);
                x=2;
        }
        for (i=x;i<=NF;i++) {
                printf ("; %s", $i);
        }
        printf ("\n");
}
$2 !~ /var[xy] *= */ {
        print;
}

Code:
# cat xx.txt
dummy3 = 7; vary= 'option1'; dummy4 = 8;
% whatever
dummy1 = 5; varx = 'false'; dummy2 = 6;
% whatever
% whatever
dummy3 = 7; vary =  'option1'; dummy4 = 8;
dummy3 = 7; vary='option1'; dummy4 = 8;
% whatever
dummy1 = 5; varx  = 'true'; dummy2 = 6;
% whatever
% whatever
dummy3 = 7; vary ='option1'; dummy4 = 8;
% whatever

Code:
# awk -f xx.awk xx.txt
dummy3 = 7;  vary= 'option1';  dummy4 = 8;
% whatever
dummy1 = 5; varx = 'false'; dummy2 = 6;
% whatever
% whatever
dummy3 = 7; vary = 'optionA';  dummy4 = 8;
dummy3 = 7; vary = 'optionA';  dummy4 = 8;
% whatever
dummy1 = 5; varx  = 'true'; dummy2 = 6;
% whatever
% whatever
dummy3 = 7; vary = 'optionB';  dummy4 = 8;
% whatever

Last edited by CarloM; 10-14-2011 at 01:04 PM..
This User Gave Thanks to CarloM For This Post:
plsrn
# 3  
Old 10-14-2011
If you insists on using sed:
Code:
sed "/varx =/h
/vary = /{
G
s/\(.*vary = '\)[^']*\('.*\)\n.*varx = 'false'.*/\1NEW_VAL_1\2/
t # optional
s/\(.*vary = '\)[^']*\('.*\)\n.*varx = 'true'.*/\1NEW_VAL_2\2/
}" file

This User Gave Thanks to binlib For This Post:
plsrn
# 4  
Old 10-16-2011
Thanks, your solution answered my question. However, you point out another problem that may appear,i.e., what happens if vary precedes varx. To better explain this point, let me express the problem in its original form, hence slightly different from the simplified one of the previous post.
I'm upgrading my personal software and for compatibility reasons I have to change all my old scripts. Striclty speaking I have the following code:

Quote:
var.applyfield1 = true; % var.applyfield1 can be true or false
% .... some line codes
var.field1type = 'type1'; % var.field1type can be one of the strings: 'type1','type2',...,'typeN'
Please, note that var.applyfield1 is a struct variable.

IF var.applyfield1 = true, at the output I want:

Quote:
var.FIELD1.APPLY = 'type1';
% .... some code lines
therefore both variable assignments regarding var.applyfield1 and var.field1type must be removed and substituted (before or after the "%... some code lines", it doesn't matter) with the new variable var.FIELD1.APPLY

ELSE, IF var.applyfield1 = false, I want:

Quote:
var.FIELD1.APPLY = '';
% .... some line codes
same as before but with a different value for var.FIELD1.APPLY (empty string).

The new problem that I was mentioning at the beginning of this reply is that awk or sed must operate as well even if var.applyfield1 and var.field1type are exchanged. For instance, with;


Quote:
var.field1type = 'type1'; % var.field1type can be one of strings: 'type1','type2',...,'typeN'
% ... some code lines
var.applyfield1 = true; % var.applyfield1 can be true or false
I want the same kind of substitution, namely:

Quote:
var.FIELD1.APPLY = 'type1';
% ...some code lines
The assignments to var.field1type and var.applyfield1 can be safely assumed to appear once in the script.

If possible, I would prefer a solution based on sed because such replacement is just one of many, which can be easily handled with the option -e.

Thanks again,
Paolo
# 5  
Old 10-17-2011
Will all substitutions involve fieldNtype and applyfieldN? (and do all occurances of those need to be replaced?)

Also, does it matter if you get:
Code:
% ...some code lines
var.FIELD1.APPLY = 'type1';

(i.e. with the new statement replacing the last of an apply/type pair) rather than the other way around?
Last edited by CarloM; 10-17-2011 at 08:26 AM.. Reason: typo
# 6  
Old 10-17-2011
Yes. Please note that field1type and applyfield1 are just generic names. You can assume that all occurances have to be replaced; if you find easier to substitute just the first occurance, for me is good as well (because each occurance appears once in my scripts).
# 7  
Old 10-17-2011
Quote:
Originally Posted by plsrn
Please note that field1type and applyfield1 are just generic names.
Obviously, but what I'm trying to determine is if there's a common pattern to the names that we can use to perform the substitution. Do they all have the form varname.somethingtype / samevarname.applysamesomething (with bold parts as fixed literals), or anything similar?
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