How can I replace a specific character in one string, with a specific character from another string?

Question

For example: I have string1 = 'abcd', and string2 = 'xwyz'.

I want to replace the 3rd character of string1 ('c') with the 4th character of string2 ('z').

Of course, string indexing starts from 0.

How can I accomplish this?

Answer 1

With bash substring manipulation:

s1="abcd"
s2="xwyz"
s1=${s1:0:2}${s2:3}${s1:3}

• ${s1:0:2} - the 1st slice containing ab (till the 3rd character c)

• ${s2:3} - the 4th character of the s2 string to be inserted

• ${s1:3} - the last (4th) character of the s1 string

---

Final s1 value:

echo $s1
abzd

---

Or with GNU awk tool:

gawk -v s2=$s2 -v FPAT='[a-z]' '{$3=substr(s2,4)}1' OFS="" <<< $s1
abzd

---

• <<< $s1 - the first string s1 is considered as input content

• -v s2=$s2 - passing the second string s2 as a variable into awk script

• FPAT='[a-z]' - regex pattern defining a field value ([a-z] - any alphabetic character)

---

Alternatively, you could also apply the "empty" field separator FS="" treating each character as separate field:

gawk -v s2=$s2 'BEGIN{ FS=OFS="" }{$3=substr(s2,4)}1' <<< $s1
abzd

Answer 2

Here is awk code (long and complicated, but work for me)

echo |awk -v a="$string1" -v b="$string2" '{split(a,a1,""); n=split(b,b1,"");a1[2]=b1[3];for (i=1;i<=n;i++) {printf a1[i]}}'