How to parse words in awk? - linux

Question

I was wondering how to parse a parragraph that looks like the following:
Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text
Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text
And many other lines with text that I do not need
* * * * * * *
Autolisp - Dialect of LISP used by the Autocad CAD package, Autodesk,
Sausalito, CA.
CPL -
1. Combined Programming Language. U Cambridge and U London. A very
complex language, syntactically based on ALGOL-60, with a pure functional
subset.
Modula-3* - Incoprporation of Modula-2* ideas into Modula-3. "Modula-3*:
So I can get the following exit from the awk sentence:
Autolisp
CPL
Modula-3*
I have tried the following sentences because the file I want to filter is huge. It is a list of all the existing programming languages so far, but basically all the lines follow the same pattern as the above
Sentences I have used so far:
BEGIN{$0 !~ /^ / && NF == 2 && $2 == "-"} { print $1 }
BEGIN{RS=""; ORS="\n\n"; FS=OFS="\n"} /^FLIP -/{print $1,$3}
BEGIN{RS=""; FS=OFS="\n"} {print $1 NF-1}
BEGIN{NF == 2 && $2 == "-" } { print $1 }
BEGIN { RS = "" } { print $1 }
The sentences that have worked for me so far are:
BEGIN { RS = "\n\n"; FS = " - " }
{ print $1 }
awk -F " - " "/ - /{ print $1 }" file.txt
But it still prints or skips lines that I need/ don't need.
Thanks for your help & response!
I have broken my head for some days because I am a rookie with AWK programming

Answer 1

The default FS should be fine, to avoid any duplicate lines you can pipe the output to sort -u
$ gawk '$2 == "-" { print $1 }' file | sort -u
Autolisp
CPL
Modula-3*
It might not filter out everything you want but you can keep adding rules until the bad data is filtered.
Alternately you can avoid using sort by using an associative array:
$ gawk '$2=="-" { arr[$1] } END { for (key in arr) print key}' file
Autolisp
CPL
Modula-3*

Answer 2

If it doesn't have to be with awk, it would probably work to first use grep to select lines of the right form, and then use sed to trim off the end, as follows:
grep -e '^.* -' | sed -e 's/\(^.*\) -.*$/\1\n/; p;'
Edit: After some playing around with awk, it looks like part of your issue is that you don't always have '[languagename] - [stuff]', but rather '[languagename] -\n[stuff]', as is the case with CPL in the sample text, and therefore, FS=" - " doesn't separate on things like that.
Also, one possible thing to try is as follows:
BEGIN { r = "^.* -"; }
{
if (match($0, r)) {
printf("%s\n", substr($0, 1, RSTART + RLENGTH - 3));
}
}
I don't actually know much about awk, but this is my best guess at replicating what the grep and sed do above. It does appear to work on the sample text you gave, at least.