replace string in a file with value from another file

Question

I have two files. One of them defines a set of number-value pairs as follows (fileA):

 1  asm
 2  assert
 3  bio
 4  bootasm
 5  bootmain
 6  buf
 7  cat
 8  console
 9  defs
10  echo

The other file contains a bunch of value pairings, as follows (fileB):

bio types
bio defs
bio param
bio spinlock
bio buf
bootasm asm
bootasm memlayout
bootasm mmu
bootmain types
bootmain elf
bootmain x86
bootmain memlayout
cat types
cat stat
cat user

I want to write a script that replaces the values on file B with their corresponding numbers from file A. It does not matter if it generates a new file or changes the existing file B.

Any ideas? Thanks

Guru · Accepted Answer · 2012-10-26 02:24:37Z

4

awk 'NR==FNR{a[$2]=$1;next}{$1=a[$1];}1' fileA fileB

NR==FNR{a[$2]=$1;next} => This is true when the fileA is processed. An associative array is formed where the index is the 2nd column with the 1st column as its value.

{$1=a[$1];} => When the second file is processed, Replace the 1st column with the appropriate value stored in the array.

1 => Print every line.

edited Oct 26, 2012 at 2:24

answered Oct 26, 2012 at 2:18

Guru

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Comments

potong · Accepted Answer · 2012-10-26 04:53:26Z

2

This might work for you (GNU sed):

sed 's|^\s*\(\S*\)\s*\(.*\)$|/^\2\\>/s//\1/|' fileA | sed -f - fileB

answered Oct 26, 2012 at 4:53

potong

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Comments

powerhouse · Accepted Answer · 2022-01-14 19:55:56Z

0

Please note the solution by @Guru doesn't work if you have undefined strings in fileB column one, for example:

fileB

...
name user
name system

will output:

...
 user
 system

The string "name" in this case will be truncated. If all rows are matched it works fine.

edited Jan 14, 2022 at 19:55

answered Jan 14, 2022 at 9:58

powerhouse

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