Question

I have a document containing { and } throughout, but I found there are mistakes. I used grep -c { * and grep -c } * to find that the number of { and } is not equal. I want to find those lines with possible errors, so I can manually check them.

• The closing braces should always appear on the same line, so I need to find lines with{ that don’t have a closing } or lines with } without the opening brace.
• Some lines have many braces, e.g. { } { } { }.
• There never should be nested braces, e.g. `{ { { } } }’.

How can I search for lines that do not have the correct number of braces?

Answer 1

You can do something like this (This will print the line and the line number) –

gawk -v FS="" '
{cnt=0;for(i=1;i<=NF;i++) if ($i=="{") ++cnt ;
else if ($i=="}") --cnt; if (cnt!=0) print NR":"$0}' file

Test:

[jaypal:~/Temp] cat file
this is {random text} some with { some without
purpose is{ to identify such lines} where { dont have a matching }
and print those lines with just one {

[jaypal:~/Temp] gawk -v FS="" '
> {cnt=0;for(i=1;i<=NF;i++) if ($i=="{") ++cnt ;
> else if ($i=="}") --cnt; if (cnt!=0) print NR":"$0}' file
1:this is {random text} some with { some without
3:and print those lines with just one {