CODEWITHSUNDEEP
bashawksed
qthas
qthas

Reputation: 1

How to change data in the first column of a file

I am trying to change in the first column of an input text two characters and doing that for multiple files -250 in this case-, using awk but I get errors. My level is beginner, so I started without including the multiple files, starting just for a single one.

Input text: *.xyz

6    -2.163968    -0.214364    0.000000
1    -1.578434    -2.353198    0.000000
1     1.575214     2.351350    0.000000
6    -4.697660     0.932898    0.000000
1    -3.168017     3.994185    0.000000
1    -5.599375     2.978998    0.000000

so the text will have different characters like 6 or 1 or more in the first column only and I want to replace only those with C for 6 and H for 1. What I try changes all of the numbers 6 and 1 or just prints error.

awk -F, -vOFS=, '{for(n=1;n<=1;n++)sub(/\6/,"C",$1)}1' *.xyz 

awk ' NF >= 4 { $(NF - 3) = "sub(/\C,"6",$1)"; print; }' *.xyz

which does not work.

What do I need to change?

Upvotes: 0

Views: 156

Answers (2)

NeronLeVelu
NeronLeVelu

Reputation: 10039

awk '{ if( $1 == 6 ) $1 = "C"; else $1 = "H"; print}' *.xyz

if space separator are important

awk '{ sub( /^6/, "C");sub( /^1/, "H"); print}' *.xyz

Upvotes: 0

amdixon
amdixon

Reputation: 3833

plan

  • use sed to in-place replace these fields

note 1.xyz and 2.xyz contain identical contents as posted in question

replace_first.sh

#!/bin/bash

for i in ./*.xyz;
do
  printf "processing $i\n";
  sed -i -e 's/^1\(\s\)/H\1/g' \
         -e 's/^6\(\s\)/C\1/g' "$i";
done;

output

$ ./replace_first.sh 
processing ./1.xyz
processing ./2.xyz
$ cat 1.xyz 
C    -2.163968    -0.214364    0.000000
H    -1.578434    -2.353198    0.000000
H     1.575214     2.351350    0.000000
C    -4.697660     0.932898    0.000000
H    -3.168017     3.994185    0.000000
H    -5.599375     2.978998    0.000000
$ cat 2.xyz 
C    -2.163968    -0.214364    0.000000
H    -1.578434    -2.353198    0.000000
H     1.575214     2.351350    0.000000
C    -4.697660     0.932898    0.000000
H    -3.168017     3.994185    0.000000
H    -5.599375     2.978998    0.000000

Upvotes: 2

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