Bash script - change value in only one column

Question

I have 1 file, for example

12341234 3,0
12341342 4,0

How can I print:

abcdabcd 3,0
abcdacdb 4,0

cat $1 | tr 1234 abcd

changes both column 1 and 2. How to change only 1 column and print all columns?

As an aside -- cat is best avoided; tr 1234 abcd <"$1" is both more reliable (works with filenames with spaces due to the corrected quoting) and faster (lets tr read straight from the input file, not from a FIFO). — Charles Duffy
– Charles Duffy, Commented Jan 21, 2018 at 18:40
@BelaVizer, eh? tr maps between character sets. The usage the OP gave works. — Charles Duffy
– Charles Duffy, Commented Jan 21, 2018 at 18:44

Charles Duffy · Accepted Answer · 2018-01-21 19:29:05Z

4

One way to do this is to split the columns and then rejoin them with paste:

paste <(cut -d' ' -f1 <"$1" | tr 1234 abcd) <(cut -d' ' -f2- <"$1")

The <() syntax for process substitution is a bashism, but the required functionality from paste, cut and tr tools is all POSIX-specified; thus, the only thing we require to run that isn't part of the POSIX standard is bash itself.

edited Jan 21, 2018 at 19:29

answered Jan 21, 2018 at 18:43

Charles Duffy

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choroba · Accepted Answer · 2018-01-21 18:43:30Z

3

Perl to the rescue:

perl -lane '$F[0] =~ tr/1234/abcd/; print "@F"' -- file

-n reads the input line by line
-l removes newlines from input and adds them to printed lines
-a splits automatically each line on whitespace into the @F array
the tr operator works similarly to tr, but you can bind it by the binding operator =~ to only operate on the first column ($F[0]).

answered Jan 21, 2018 at 18:43

choroba

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Cyrus · Accepted Answer · 2018-01-21 18:44:53Z

2

With GNU sed:

sed 'h;s/.* //;x;s/ .*//;y/1234/abcd/;G;s/\n/ /' file

Output:

abcdabcd 3,0
abcdacdb 4,0

See: man sed

answered Jan 21, 2018 at 18:44

Cyrus

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RomanPerekhrest · Accepted Answer · 2018-01-21 18:56:19Z

0

Awk solution:

awk 'BEGIN{ split("abcd", a, "") }
     { 
         len=split($1, b, ""); 
         for (i=1; i<=len; i++) printf("%s",(b[i] in a? a[b[i]] : b[i])); 
         print FS $2 
     }'  file

The output:

abcdabcd 3,0
abcdacdb 4,0

answered Jan 21, 2018 at 18:56

RomanPerekhrest

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