#!/usr/bin/env bash
# Desc: Removes lines that aren't audio file paths
# Usage: find . -type f | isAudio
# Input: stdin
# Output: stdout
# Version: 0.0.1
# Example: find ~/Music/ -type f | isAudio | mpv --playlist=-
# Depends:
# BK-2020-03: read_stdin() 0.0.1
declare -a music_codecs # Array for storing valid codec names (e.g. "aac" "mp3")
# Adjustable parameters
music_codecs=("vorbis" "aac" "mp3" "flac" "opus"); # whitelist of valid codec_names ffprobe might return
yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
read_stdin() {
# Desc: Consumes stdin; outputs as stdout lines
# Input: stdin (consumes)
# Output: stdout (newline delimited)
# Example: printf "foo\nbar\n" | read_stdin
# Depends: GNU bash (version 5.1.16)
# Version: 0.0.1
local input_stdin output;
# Store stdin
if [[ -p /dev/stdin ]]; then
input_stdin="$(cat -)";
fi;
# Store as output array elements
## Read in stdin
if [[ -n $input_stdin ]]; then
while read -r line; do
output+=("$line");
done < <(printf "%s\n" "$input_stdin");
fi;
# Print to stdout
printf "%s\n" "${output[@]}";
}; # read stdin to stdout lines
check_parsable_audio_ffprobe() {
# Desc: Checks if ffprobe returns valid audio codec name for file
# Usage: check_parsable_audio_ffprobe [path FILE]
# Version: 0.0.1
# Input: arg1: file path
# Output: exit code 0 if returns valid codec name; 1 otherwise
# Depends: ffprobe, die()
local file_in ffprobe_out
if [[ $# -ne 1 ]]; then die "ERROR:Invalid number of args:$#"; fi;
file_in="$1";
# Check if ffprobe detects an audio stream
if ffprobe -v error -select_streams a -show_entries stream=codec_name -of default=nokey=1:noprint_wrappers=1 "$file_in" 1>/dev/null 2>&1; then
return_state="true";
else
return_state="false";
fi;
# Fail if ffprobe returns no result
ffprobe_out="$(ffprobe -v error -select_streams a -show_entries stream=codec_name -of default=nokey=1:noprint_wrappers=1 "$file_in")";
if [[ -z $ffprobe_out ]]; then
return_state="false";
fi;
# Report exit code
if [[ $return_state = "true" ]]; then
return 0;
else
return 1;
fi;
} # Checks if file has valid codec name using ffprobe
get_audio_format() {
# Desc: Gets audio format of file as string
# Usage: get_audio_format arg1
# Depends: ffprobe
# Version: 0.0.1
# Input: arg1: input file path
# Output: stdout (if valid audio format)
# exit code 0 if audio file; 1 otherwise
# Example: get_audio_format myvideo.mp4
# Note: Would return "opus" if full ffprobe report had 'Audio: opus, 48000 Hz, stereo, fltp'
# Note: Not tested with videos containing multiple video streams
# Ref/Attrib: [1] https://stackoverflow.com/questions/5618363/is-there-a-way-to-use-ffmpeg-to-determine-the-encoding-of-a-file-before-transcod
# [2] https://stackoverflow.com/questions/44123532/how-to-find-out-the-file-extension-for-extracting-audio-tracks-with-ffmpeg-and-p#comment88464070_50723126
local audio_format file_in;
local return_state;
file_in="$1";
# Return error exit code if not audio file
## Return error if ffprobe itself exited on error
if ! ffprobe -v error -select_streams a -show_entries stream=codec_name -of default=nokey=1:noprint_wrappers=1 "$file_in" 1>/dev/null 2>&1; then
return_state="false";
fi;
# Get audio format
audio_format="$(ffprobe -v error -select_streams a -show_entries stream=codec_name -of default=nokey=1:noprint_wrappers=1 "$file_in")"; # see [1]
## Return error if audio format is incorrectly formatted (e.g. reject if contains spaces)
pattern="^[[:alnum:]]+$"; # alphanumeric string with no spaces
if [[ $audio_format =~ $pattern ]]; then
return_state="true";
# Report audio format
echo "$audio_format";
else
return_state="false";
fi;
# Report exit code
if [[ $return_state = "true" ]]; then
return 0;
else
return 1;
fi;
} # Get audio format as stdout
checkIsInArray() {
# Desc: Checks if input arg is element in array
# Usage: checkIsInArray arg1 arg2
# Version: 0.0.1
# Input: arg1: test string
# arg2: array
# Output: exit code 0 if test string is in array; 1 otherwise
# Example: checkIsInArray "foo" "${myArray[@]}"
# Ref/Attrib: [1] How do I check if variable is an array? https://stackoverflow.com/a/27254437
# [2] How to pass an array as function argument? https://askubuntu.com/a/674347
local return_state input arg1 string_test
declare -a arg2 array_test
input=("$@") # See [2]
arg1="${input[0]}";
arg2=("${input[@]:1}");
#yell "DEBUG:input:${input[@]}";
#yell "DEBUG:arg1:${arg1[@]}";
#yell "DEBUG:arg2:${arg2[@]}";
string_test="$arg1";
array_test=("${arg2[@]}");
#yell "DEBUG:string_test:$string_test";
#yell "DEBUG:$(declare -p array_test)";
for element in "${array_test[@]}"; do
#yell "DEBUG:element:$element";
if [[ "$element" =~ ^"$string_test" ]]; then
return_state="true";
continue;
fi;
done;
# Report exit code
if [[ $return_state == "true" ]]; then
return 0;
else
return 1;
fi;
} # Check if string is element in array
check_depends() {
if ! command -v ffprobe 1>/dev/random 2>&1; then
die "FATAL:Missing ffprobe."; fi;
};
main() {
# Input: array: music_codecs ("mp3" "aac" ...)
# stdin
# Output: stdout
# Depends:
# BK-2020-03: read_stdin() 0.0.1
# check dependencies
check_depends;
# iterate through stdin lines
while read -r line; do
# check if file
if [[ ! -f $line ]]; then continue; fi; # reject
# check if valid codec
if ! check_parsable_audio_ffprobe "$line"; then
continue; fi; # reject
# Check if desired codec
file_format="$(get_audio_format "$line")";
if ! checkIsInArray "$file_format" "${music_codecs[@]}"; then
continue; fi; # reject
# Output line to stdout
printf "%s\n" "$line";
done < <(read_stdin);
}; # main program
main "$@" 2>/dev/random;
# Author: Steven Baltakatei Sandoval
# License: GPLv3+