определить тип файла (determine file type)
Статус выхода (Exit)
file will exit with 0 if the operation was successful or >0 if an
error was encountered. The following errors cause diagnostic
messages, but don't affect the program exit code (as POSIX
requires), unless -E is specified:
• A file cannot be found
• There is no permission to read a file
• The file type cannot be determined
