How can I repeat a character in bash?

Question

How could I do this with echo?

perl -E 'say "=" x 100'

Answer 1

function repeatString()
{
    local -r string="${1}"
    local -r numberToRepeat="${2}"

    if [[ "${string}" != '' && "${numberToRepeat}" =~ ^[1-9][0-9]*$ ]]
    then
        local -r result="$(printf "%${numberToRepeat}s")"
        echo -e "${result// /${string}}"
    fi
}

Sample runs

$ repeatString 'a1' 10 
a1a1a1a1a1a1a1a1a1a1

$ repeatString 'a1' 0 

$ repeatString '' 10 

Reference lib at: https://github.com/gdbtek/linux-cookbooks/blob/master/libraries/util.bash

Answer 2

In case that you want to repeat a character n times being n a VARIABLE number of times depending on, say, the length of a string you can do:

#!/bin/bash
vari='AB'
n=$(expr 10 - length $vari)
echo 'vari equals.............................: '$vari
echo 'Up to 10 positions I must fill with.....: '$n' equal signs'
echo $vari$(perl -E 'say "=" x '$n)

It displays:

vari equals.............................: AB  
Up to 10 positions I must fill with.....: 8 equal signs  
AB========  

Answer 3

There's more than one way to do it.

Using a loop:

• Brace expansion can be used with integer literals:

  for i in {1..100}; do echo -n =; done    
  

• A C-like loop allows the use of variables:

  start=1
  end=100
  for ((i=$start; i<=$end; i++)); do echo -n =; done
  

Using the printf builtin:

printf '=%.0s' {1..100}

Specifying a precision here truncates the string to fit the specified width (0). As printf reuses the format string to consume all of the arguments, this simply prints "=" 100 times.

Using head (printf, etc) and tr:

head -c 100 < /dev/zero | tr '\0' '='
printf %100s | tr " " "="

Answer 4

I guess the original purpose of the question was to do this just with the shell's built-in commands. So for loops and printfs would be legitimate, while rep, perl, and also jot below would not. Still, the following command

jot -s "/" -b "\\" $((COLUMNS/2))

for instance, prints a window-wide line of \/\/\/\/\/\/\/\/\/\/\/\/

Answer 5

Simplest is to use this one-liner in csh/tcsh:

printf "%50s\n" '' | tr '[:blank:]' '[=]'

---

Answer 6

repeat() {
    # $1=number of patterns to repeat
    # $2=pattern
    printf -v "TEMP" '%*s' "$1"
    echo ${TEMP// /$2}
}