feat(user/mp4_make480.sh):Add script to convert video to 480 res
[BK-2020-03.git] / 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 "$@";