How to join words as below in bash

Question

I have a file, words.txt on a Linux machine, containing the following lines. How can I repeat each of the strings user, apple and banana, appending a number from 1 to 4 to them?

user
apple
banana

Expected Output :

user1
user2
user3
user4
apple1
apple2
apple3
apple4
banana1
banana2
banana3
banana4

I tried the following but only worked with 1 string.

seq 1 4 | awk {'print $0 "user"'}

Answer 1

awk in the standard toolchest is probably your best bet here.

awk -v min=1 -v max=4 -v increment=1 '
  {for (i = min; i <= max; i += increment) print $0 i}' words.txt

With GNU tools, taking inspiration from @JJoao's approach at taking the cartesion product of the lines of two files:

join -t $'\n' -j2 -o1.1,2.1 words.txt <(seq 4) | paste -d '\0' - -

Where we join words.txt and the output of seq 4 on the second field, but here as we define the field delimiter as newline, there can't be a second field, or in other words, the second field is empty for every line of both files, so we end up joining everything together.

Answer 2

sed 's/.*/&1\n&2\n&3\n&4/' words.txt

We are replacing (s command) everything on each line (.*), with the whole match (&) appearing multiple times with the literal numbers and newlines added.

Answer 3

With plain bash:

while IFS= read -r word; do printf "${word}%d\\n" {1..4}; done < words.txt

However, putting a variable in the printf format string makes it vulnerable to unexpected characters. For example:

$ cat words.txt
with \n newline
with %s directive

$ while IFS= read -r word; do printf "${word}%d\\n" {1..4}; done < words.txt
with
 newline1
with
 newline2
with
 newline3
with
 newline4
with 1 directive2
with 3 directive4

Backslash sequences will be interpreted, and % directives will be obeyed. To protect this, the simple one-line solution becomes:

while IFS= read -r word; do
    tmp1=${word//%/%%}
    tmp2=${tmp1//\\/\\\\}
    printf "${tmp2}%d\\n" {1..4}
done < words.txt

which outputs

with \n newline1
with \n newline2
with \n newline3
with \n newline4
with %s directive1
with %s directive2
with %s directive3
with %s directive4

Answer 4

% perl -nE 'chomp; for $c (1..4) { say "$_ $c"}' words.txt

Explanation:

• perl -n .... words.txt will loop over all lines in words.txt, setting the variable $_ to the current line
• -E '....' specifies the code to run for each line of input
  • chomp removes newline at the end of $_
  • for $c (1..4) will iterate variable $c from 1 to 4, running the code inside { .... }
    • say "$_ $c" will print our input line (word user, apple etc.) followed by space and counter $c.

so running it would result in:

user 1
user 2
user 3
user 4
apple 1
apple 2
apple 3
apple 4
banana 1
banana 2
banana 3
banana 4

Answer 5

If your file really is just 4 lines long you could do something simple like:

$ while read word; do seq 1 4 | awk -v w="$word" '{print w$0}'; done < words.txt 
user1
user2
user3
user4
apple1
apple2
apple3
apple4
banana1
banana2
banana3
banana4

But it is not a good idea to use the shell for things like this, so here's a native GNU awk (because it keeps the original order) solution:

$ gawk '{ words[$0] }END{for (word in words){ for(i=1;i<5;i++){printf "%s%d\n",word,i}}}' words.txt 
user1
user2
user3
user4
apple1
apple2
apple3
apple4
banana1
banana2
banana3
banana4

This awk approach needs to read the whole file into memory. Stéphane's answer is a much better solution, I recommend you use that one instead.

Answer 6

for  j in $(cat file.txt); do for ((z=1;z<=4;z++)); do echo "$j$z" >>final.txt; done; done

output

user1
user2
user3
user4
apple1
apple2
apple3
apple4
banana1
banana2
banana3
banana4

Answer 7

How about:

for i in $(cat file.txt); do for j in $(seq 1 4); do echo ${i}${j}; done; done

This gives:

user1
user2
user3
user4
apple1
apple2
apple3
apple4
banana1
banana2
banana3
banana4

Answer 8

Pipe the file to xargs and use bash to execute your command for every word in it:

$ cat words.txt | xargs -I % bash -c "seq 1 4 | awk {'print \"%\"\$0'}"
user1
user2
user3
user4
apple1
apple2
apple3
apple4
banana1
banana2
banana3
banana4

Note that you need to escape with a backslash the double quote and dollar sign characters within the command's double quotes.