Replace a field only for lines beginning with a string with a defined string

Question

Here is the file I need to deal with.

ENR1;203023;0000;H606626;001505;EL;00;1234;0000100;00;00;201346100;H6022418;
ENR6;000218;130155;000;00;201443;000000000;000000000;000000000;000000000;
ENR1;203357;0000;H606626;001653;EL;01;2546;0000800;00;00;201346100;H6022418;
ENR6;000218;130155;000;00;201503;000000000;000000000;000000000;000000000;
ENR6;001811;150316;000;00;201624;000000000;000000000;000000000;000000000;
ENR1;203385;0000;H606625;000615;EL;00;5861;0000100;00;00;201346100;H6022418;

I must substitute field 7 of each line. If the value is 00, then I must set it to 01. But only for lines whose first field is ENR1!

awk -F';' -v OFS=';' 'NR>=1{sub("00","01",$7)}1' file > result

This works but also remplace field $7 with lines beginning with ENR6.

How adding the condition (only lines starting with ENR1?)

Answer 1

I would try

awk -F';' -v OFS=';' '$7 == "00" && $1 == "ENR1" { $7 = "01" } {print} ' file > result

where

• $7 == "00" && $1 == "ENR1" { $7 = "01" } only applied to line starting with ENR1, having seventh field equel to 00
• $7 = "01" set 7th field to 01

• { print } print every line, including ENR1's after change.

• you may wish to keep NR>=1 test if real file has a one-line header.

Answer 2

Short sed approach:

sed -E 's/^(ENR1;([^;]+;){5})00;/\101;/' file

The output:

ENR1;203023;0000;H606626;001505;EL;01;1234;0000100;00;00;201346100;H6022418;
ENR6;000218;130155;000;00;201443;000000000;000000000;000000000;000000000;
ENR1;203357;0000;H606626;001653;EL;01;2546;0000800;00;00;201346100;H6022418;
ENR6;000218;130155;000;00;201503;000000000;000000000;000000000;000000000;
ENR6;001811;150316;000;00;201624;000000000;000000000;000000000;000000000;
ENR1;203385;0000;H606625;000615;EL;01;5861;0000100;00;00;201346100;H6022418;

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• ^(ENR1;([^;]+;){5})00; - captures lines starting with ENR1 followed by 5 fields ([^;]+;){5} and the 7th field 00;