awk only change matching line and print rest of lines without modification - perl

Question

So I have a large file like the following:
RESOURCETAGMAPPINGLIST arn:aws:ec2:us-east-1:XXXXXX:instance/i-XXXXXXXXXXXXXXXXX
TAGS app-name appname1
RESOURCETAGMAPPINGLIST arn:aws:ec2:us-east-1:XXXXXX:instance/i-XXXXXXXXXXXXXXXXX
TAGS app-name appname2
RESOURCETAGMAPPINGLIST arn:aws:ec2:us-east-1:XXXXXX:instance/i-XXXXXXXXXXXXXXXXX
TAGS app-name appname1
..
I only want to modify the line with RESOURCETAGMAPPINGLIST and print the the other lines w/out modification. Then I want to print only specific fields on the matching like, like below:
arn ec2 us-east-1 XXXXXX
TAGS app-name appname1
arn ec2 us-east-1 XXXXXX
TAGS app-name appname2
arn ec2 us-east-1 XXXXXX
TAGS app-name appname1
..
I was trying using awk gsub command, but really could not get the -F: part to work out. Any help would be greatly appreciated and it does not matter if it's awk, sed or perl.

Answer 1

With awk. I used as input field separators at least one space ( +) or (|) one colon (:).
If a row contains string RESOURCETAGMAPPINGLIST then print columns 2, 4, 5, 6 and stop processing this row and continue with next row. If a row does not contain RESOURCETAGMAPPINGLIST then print complete row unchanged.
awk -F ' +|:' '/RESOURCETAGMAPPINGLIST/{print $2,$4,$5,$6; next} {print}' file
Output:
arn ec2 us-east-1 XXXXXX
TAGS app-name appname1
arn ec2 us-east-1 XXXXXX
TAGS app-name appname2
arn ec2 us-east-1 XXXXXX
TAGS app-name appname1
See: The Stack Overflow Regular Expressions FAQ

Answer 2

One awk idea using the default field delimiter and split():
awk '
/RESOURCETAGMAPPINGLIST/ { split($2,a,":") # split 2nd field on ":" delimiter, storing results in array a[]
print a[1],a[3],a[4],a[5]
next # skip to next line of inpu
}
1 # print current line
' sample.dat
# or as a one-liner sans comments:
awk '/RESOURCETAGMAPPINGLIST/ {split($2,a,":"); print a[1],a[3],a[4],a[5]; next} 1' sample.dat
This generates:
arn ec2 us-east-1 XXXXXX
TAGS app-name appname1
arn ec2 us-east-1 XXXXXX
TAGS app-name appname2
arn ec2 us-east-1 XXXXXX
TAGS app-name appname1

Answer 3

Here is one way to do it:
#!/usr/bin/perl
use v5.30; # Perl v5.10 or above is required to use 'say' instead of 'print'
use warnings;
my $file = "datafile.txt"; #declare file name
open( my $fh, "<", $file ) or die( "Can't open `$file`: $!\n" );
#open the file with file handle $fh
while (my $line = <$fh>){ #read the file line by line
chomp $line; #remove line breaks
if ($line =~ m/^RESOURCETAGMAPPINGLIST/){ #if line start with
my #fields = split(/\t|:/, $line); #split in tab or : characters; each field becomes an element of #fields array
say (join ' ', (#fields[1,2,3,4])); #join the relevant fields with a single space and print
}else{
say $line; #if line does not start with RESOURCETAGMAPPINGLIST, simply print it
}
}
#when script finishes, Perl will automatically close the input file.

Answer 4

I assume that one keeps the fields 1,3,4,5 from the colon-separated part.
perl -wple'
s{^RESOURCETAGMAPPINGLIST\s+(.+)}
{ join " ", ( $1 =~ /([^:]+)/g )[0,2..4] }e' file
With -p the variable $_, which has the line to process, is printed after the processing.
If that keyword isn't matched the regex does nothing and $_ remains unchanged. If it matches then the whole line does and it, so $_, gets replaced with the return of the code in the replacement side. (With /e modifier the replacement side is evaluated as code, which extracts the select words separated by : in the rest of the line, captured in $1, and joins them by space.)
Or: test for the word, and either split the line and join the needed parts or print it as is
perl -wnlE'say
/^RESOURCETAGMAPPINGLIST/ ? join " ", (split /\s+|:/)[1,3..5] : $_' file
These are broken into lines so they are easier to read. They can be copy-pasted as they are (in bash), or brought onto one line. Or, this can be written far more nicely in a file, but the question seems to be asking for a command-line program.

Answer 5

This might work for you (GNU sed):
sed -E 's/^RESOURCETAGMAPPINGLIST *([^:]+):[^:]+:([^:]+):([^:]+):([^:]+).*/\1 \2 \3 \4/' file
Pattern match and reformat as required.