mjhjmtu

For example, the only thing in file.txt looks like this:

xxxxxxxxxHAHAxxxxxxHOHOxxxxxxx 

I hope to replace HAHA with seq 1 3 and replace HOHO with seq 5 7, so the output should be:

xxxxxxxxx1xxxxxx5xxxxxxx 
xxxxxxxxx2xxxxxx6xxxxxxx 
xxxxxxxxx3xxxxxx7xxxxxxx 

What I did:

for i in $(seq 1 3) 
do sed "s/HAHA/$i/g" file.txt 
 for i in $(seq 5 7) 
 do sed "s/HOHO/$i/g" file.txt 
 done 
done > new.txt 

But new.txt doesn't show what I expected. How should I change the code?

Here's one way you could do it, using the bash built-in read command's ability to read from different file descriptors:

while read -u3 i && read -u4 j; do 
 sed -e "s/HAHA/$i/" -e "s/HOHO/$j/" file.txt
done > new.txt 3< <(seq 1 3) 4< <(seq 5 7)

Since your numbers have a simple arithmetic relationship, it would be simpler to use a single seq process + some shell arithmetic:

for i in $(seq 1 3); do
 sed -e "s/HAHA/$i/" -e "s/HOHO/$((i+4))/" file.txt
done > new.txt

In either case, see Why is using a shell loop to process text considered bad practice? - the inefficiencies may not matter for the minimal example you have provided, but if you are doing anything more serious you should consider using a different approach.

Without calling an external utility for each line produced:

read template <file

paste <(seq 1 3) <(seq 5 7) |
while read x y; do
 t=$template/HAHA/$x
 t=$t/HOHO/$y
 printf '%sn' "$t"
done >new.txt

This first reads the line from the file called file into $template. It then constructs a two-column input for a while read loop. The input to the loop is the two columns of numbers from seq.

In the loop, some bash-specific substitutions are performed on the value of $template to replace the HAHA and HOHO string with the numbers read from paste. This creates $t which is then outputted.

Using only awk, and assuming that the input is a single line only:

awk '
 for (i = 1; i <= 3; ++i) 
 t = $0;
 sub("HAHA", i, t)
 sub("HOHO", 4+i, t)
 print t
 
 ' file

A shell loop for bash, mimicking the awk code above:

read template <file

for (( i = 1; i <= 3; ++i )); do
 t=$template/HAHA/$i
 t=$t/HOHO/$((i+4))
 printf '%sn' "$t"
done