Find the location of a dependency program

Each of these functions returns the location of one program as a string: find_ffmpeg(), find_ffprobe(), find_ffplay() and find_mediainfo().

Usage

find_ffmpeg()

find_mediainfo()

find_ffprobe()

find_ffplay()

Value

The location of the program as a string, or NULL when it could not be found.

Details

The function looks on the PATH first. If the program is not there, the function reads the location that set_program() saved. That location is in a file under tools::R_user_dir("tidymedia", "config"). If neither place has the program, the function gives a warning and returns NULL.

Problems with a saved location

A saved location that no longer works gives a warning, and the function returns NULL. The warning has one of two classes that you can catch:

• tidymedia_location_gone: the function read the location, but no program is there now. The condition holds the program name in tm_program and the location in tm_location.

• tidymedia_location_unreadable: the file does not hold exactly one location. It is empty, has more than one line, or has one empty line. The condition holds the program name in tm_program and the file in tm_file.

A line that holds only spaces counts as a location. So it gives tidymedia_location_gone, not tidymedia_location_unreadable.

To fix either problem, forget the location with unset_program(), or replace it with set_program().

Locations saved by earlier versions

Versions of the package before 0.2.0 saved locations in a different folder, rappdirs::user_config_dir("tidymedia", "R"). The functions still read a file in that folder. They read it only when the current folder has no file for the program. program_status() looks in the same places, in the same order.

A tidymedia_location_unreadable warning names the file that the function read. That file can be the one in the old folder.

set_program() writes to the current folder only. After it writes a file for a program, the old file for that program is not read.

unset_program() removes the file in both folders. So the old location does not come back after the current file is gone.

See also

set_program() to save the location of a program that is not on the PATH, and install_on_win() to download FFmpeg on Windows.

Other program management functions: install_on_win(), program_status(), set_program(), unset_program()

Examples

# Returns the path to the binary, or NULL with a warning if it is not found
find_ffmpeg()
#>            ffmpeg 
#> "/usr/bin/ffmpeg" 
find_mediainfo()
#>            mediainfo 
#> "/usr/bin/mediainfo"