unitproc/get_rand_line

   1 #!/usr/bin/env bash
   2 # Desc: Gets random line from a newline-delimited file
   3 # Usage: get_rand_line [path FILE]
   4 # Version: 0.0.1
   5
   6 yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
   7 die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
   8 must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
   9 get_rand_line() {
  10     # Input: arg1 : file path
  11     #        stdout: random line from input file
  12     # Usage: get_rand_line [path FILE]
  13     # Depends: GNU Coreutils 8.32 (shuf)
  14
  15     # Check if file
  16     if [[ ! -f "$1" ]]; then die "FATAL:Not a file:$1"; fi;
  17     if [[ $# -ne 1 ]]; then die "FATAL:Incorrect argument count:$1"; fi;
  18
  19     # Get line count
  20     lc="$(wc -l "$1" | awk '{print $1}')";
  21
  22     # Calc random line number (zero-indexed)
  23     ln="$(shuf -i 0-"$((lc - 1))" -n1)";
  24
  25     n=0;
  26     while read -r line; do
  27         # Check if line is target line
  28         if [[ $n -eq $ln ]]; then
  29             printf "%s\n" "$line"; # output
  30         fi;
  31         ((n++));
  32     done < "$1";
  33 }; # Returns random line from newline-delimited file
  34 main() {
  35     get_rand_line "$@";
  36 };
  37
  38 main "$@";