GNU 中的递归通配符 make？

我已经有一段时间没有使用 make了，所以请耐心等待..。

我有一个目录，flac，包含。FLAC 文件。我有一个相应的目录，mp3包含 MP3文件。如果 FLAC 文件比相应的 MP3文件更新(或者相应的 MP3文件不存在) ，那么我想运行一系列命令将 FLAC 文件转换成 MP3文件，然后复制标签。

意外的是: 我需要递归地搜索 flac目录，并在 mp3目录中创建相应的子目录。目录和文件可以在名称中使用空格，并以 UTF-8命名。

我想用 make来驱动它。

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最佳答案

I would try something along these lines

FLAC_FILES = $(shell find flac/ -type f -name '*.flac')
MP3_FILES = $(patsubst flac/%.flac, mp3/%.mp3, $(FLAC_FILES))


.PHONY: all
all: $(MP3_FILES)


mp3/%.mp3: flac/%.flac
@mkdir -p "$(@D)"
@echo convert "$<" to "$@"

A couple of quick notes for make beginners:

  • The @ in front of the commands prevents make from printing the command before actually running it.
  • $(@D) is the directory part of the target file name ($@)
  • Make sure that the lines with shell commands in them start with a tab, not with spaces.

Even if this should handle all UTF-8 characters and stuff, it will fail at spaces in file or directory names, as make uses spaces to separate stuff in the makefiles and I am not aware of a way to work around that. So that leaves you with just a shell script, I am afraid :-/

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FWIW, I've used something like this in a Makefile:

RECURSIVE_MANIFEST = `find . -type f -print`

The example above will search from the current directory ('.') for all "plain files" ('-type f') and set the RECURSIVE_MANIFEST make variable to every file it finds. You can then use pattern substitutions to reduce this list, or alternatively, supply more arguments into find to narrow what it returns. See the man page for find.

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You can define your own recursive wildcard function like this:

rwildcard=$(foreach d,$(wildcard $(1:=/*)),$(call rwildcard,$d,$2) $(filter $(subst *,%,$2),$d))

The first parameter ($1) is a list of directories, and the second ($2) is a list of patterns you want to match.

Examples:

To find all the C files in the current directory:

$(call rwildcard,.,*.c)

To find all the .c and .h files in src:

$(call rwildcard,src,*.c *.h)

This function is based on the implementation from this article, with a few improvements.

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My solution is based on the one above, uses sed instead of patsubst to mangle the output of find AND escape the spaces.

Going from flac/ to ogg/

OGGS = $(shell find flac -type f -name "*.flac" | sed 's/ /\\ /g;s/flac\//ogg\//;s/\.flac/\.ogg/' )

Caveats:

  1. Still barfs if there are semi-colons in the filename, but they're pretty rare.
  2. The $(@D) trick won't work (outputs gibberish), but oggenc creates directories for you!
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If you're using Bash 4.x, you can use a new globbing option, for example:

SHELL:=/bin/bash -O globstar
list:
@echo Flac: $(shell ls flac/**/*.flac)
@echo MP3: $(shell ls mp3/**/*.mp3)

This kind of recursive wildcard can find all the files of your interest (.flac, .mp3 or whatever). O

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Here's a Python script I quickly hacked together to solve the original problem: keep a compressed copy of a music library. The script will convert .m4a files (assumed to be ALAC) to AAC format, unless the AAC file already exists and is newer than the ALAC file. MP3 files in the library will be linked, since they are already compressed.

Just beware that aborting the script (ctrl-c) will leave behind a half-converted file.

I originally also wanted to write a Makefile to handle this, but since it cannot handle spaces in filenames (see the accepted answer) and because writing a bash script is guaranteed to put in me in a world of pain, Python it is. It's fairly straightforward and short, and thus should be easy to tweak to your needs.

from __future__ import print_function




import glob
import os
import subprocess




UNCOMPRESSED_DIR = 'Music'
COMPRESSED = 'compressed_'


UNCOMPRESSED_EXTS = ('m4a', )   # files to convert to lossy format
LINK_EXTS = ('mp3', )           # files to link instead of convert




for root, dirs, files in os.walk(UNCOMPRESSED_DIR):
out_root = COMPRESSED + root
if not os.path.exists(out_root):
os.mkdir(out_root)
for file in files:
file_path = os.path.join(root, file)
file_root, ext = os.path.splitext(file_path)
if ext[1:] in LINK_EXTS:
if not os.path.exists(COMPRESSED + file_path):
print('Linking {}'.format(file_path))
link_source = os.path.relpath(file_path, out_root)
os.symlink(link_source, COMPRESSED + file_path)
continue
if ext[1:] not in UNCOMPRESSED_EXTS:
print('Skipping {}'.format(file_path))
continue
out_file_path = COMPRESSED + file_path
if (os.path.exists(out_file_path)
and os.path.getctime(out_file_path) > os.path.getctime(file_path)):
print('Up to date: {}'.format(file_path))
continue
print('Converting {}'.format(file_path))
subprocess.call(['ffmpeg', '-y', '-i', file_path,
'-c:a', 'libfdk_aac', '-vbr', '4',
out_file_path])

Of course, this can be enhanced to perform the encoding in parallel. That is left as an exercise to the reader ;-)


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