Create a file of a specific size with random printable strings in bash

Question

I want to create a file of a specific size containing only printable strings in bash.

My first thought was to use /dev/urandom:

dd if=/d         


        

Answer 1

A conversion of @MarekNowaczyk answer to plain bash:

#!/bin/sh
(( $# )) || {  echo "Pass file size as initial parameter" >&2; exit 1; }
size=$1
mk_range(){ name=$1; shift; printf -v "$name" '%b' "$(printf '\\U%08x' "$@")"; }
add_chars(){ local var; mk_range var "$@"; chars+=$var; }
    ## uncomment following lines to use each range.
    add_chars {48..57}    # 0-9 numbers
    add_chars {65..90}    # A-Z LETTERS
    add_chars {97..122}   # a-z letters
    add_chars {32,{33..47},{58..64},{91..96},{123..127}}     # other chars.
    # convert list of characters to an array of characters.
    [[ $chars =~ ${chars//?/(.)} ]] && arr=("${BASH_REMATCH[@]:1}");
    alphabet_len=${#arr[@]} 
    # loop to print random characters
    for ((i=0;i<$size;i++)); do
        idx=$((RANDOM%alphabet_len))
        printf '%s' "${arr[idx]}"
    done
    # Add a trailing new line.
    echo

This code does not ensure that the resulting random distribution is uniform, it was written as an example. To ensure a random distribution in the output, we would have to use careful arbitrary precision arithmetic to change the base (count of output characters).
Also, RANDOM is not a CSPRNG.