Modify bash string

Question

I am new in bash and need help in this problem.

#!/bin/bash

str="This Is My Bash String"
mod="-val"

# Loop through characters of str. If index is 0, insert mod at position 0. And if the current index contains space (" "), then insert mod after the space.

echo -e str
# This should output: -valThis -valIs -valMy -valBash -valString

How can I achieve this?

score 7 · Answer 1 · answered Aug 21 '21 at 09:44

7

With bash and Parameter Expansion:

echo "$mod${str// / $mod}"

Output:

-valThis -valIs -valMy -valBash -valString

answered Aug 21 '21 at 09:44

Cyrus

84,225
14
89
153

score 2 · Accepted Answer · answered Aug 21 '21 at 08:37

2

for word in $str
do echo -n " $mod$word"
done

answered Aug 21 '21 at 08:37

user2683246

3,399
29
31

This is not the recommended way to split a string. See: https://stackoverflow.com/a/918931/7939871 `IFS=' ' read -ra words <<< "$str"; for word in "${words[@]}"; do` … – Léa Gris Aug 21 '21 at 11:51

score 1 · Answer 3 · answered Aug 21 '21 at 11:44

1

This might also do the job:

echo $mod$str |sed -e "s/ / $mod/g"

answered Aug 21 '21 at 11:44

biwiki

62
3

score 1 · Answer 4 · answered Aug 21 '21 at 12:01

Alternative to parameter expansion:

#!/usr/bin/env bash

str="This Is My Bash String"
mod="-val"

# Split string words into an array
IFS=' ' read -ra splitstr <<<"$str"

# Print each element of array, prefixed by $mod
printf -- "$mod%s " "${splitstr[@]}"
printf \\n

score 1 · Answer 5 · answered Aug 21 '21 at 13:17

build_command_line() {
  local -ar tokens=(${@:2})
  printf '%s\n' "${tokens[*]/#/"$1"}"
}

Now let’s test it a bit:

mod='-val'
str='This Is My Bash String'

build_command_line "$mod" "$str"
build_command_line "$mod" $str
build_command_line "$mod" "$str" Extra Tokens
build_command_line "$mod" $str 'Extra Tokens'

To “modify” str, as you specify, just reassign it:

str="$(build_command_line "$mod" "$str")"
printf '%s\n' "$str"

Modify bash string

5 Answers5