This question already has answers here:
How can I use inverse or negative wildcards when pattern matching in a unix/linux shell?
(11 answers)
Closed 5 years ago.
I have a folder of audio files. Most are single sounds -- or soundSprites -- while some are several soundSprites concatenated into spriteLists. These spriteLists use a naming convention with a _SL added to the end of the file name. How can I create two arrays of soundSprites and spriteLists? I've tried using find to exclude the spriteLists like so:
soundSprites+=($(find . -maxdepth 1 ! -name "*_SL*"))
But this adds a ./ before every file name which I want to avoid. Instead of figuring out how to then iterate through the array and remove every ./ I can only assume there's an elegant solution to this that I'm simply unaware of.
Any help is greatly appreciated.
Don't use find here; this will fail for file names that contain characters the shell will use for word-splitting or pathname generation. Instead, use a pattern designed for pathname generation.
shopt -s extglob
soundSprites+=( !(*_SL*) )
With the information from the best answer of this question:
How can I use inverse or negative wildcards when pattern matching in a unix/linux shell?
you can do:
shopt extglob
soundSprites=(!(*_SL*))
Related
Command ffmpeg -i file-1.mp4 -vf ass=file-1a.ass burned-1.mp4
works to burn file-1a.ass subtitles on file-1.mp4 video.
But each time I have to reiterate the same command on over 40 different videos and subtitles and each time I have to wait for rendering the output.
So perhaps there is a way to automatically reiterate the same command on all the files.
Looking for a reply found the loop command
for f in *; do ffmpeg $f;
But I am confused how to use it with 2 files, the .mp4 and the .ass file, and also the output file which should have the same number
I imagine should put the same name on each couple of files, such as:
1.mp4 1.ass
2.mp4 2.ass
3.mp4 3.ass
etc
and then
for f in *; do ffmpeg -i $f.mp4 -vf ass=$f.ass $f-output.mp4
But I have no clear idea
You have the right idea. But it won’t work if the loop executes with f == 1.mp4, then again with f == 1.ass, and so on.
So you want to modify the loop to only iterate over .mp4 files. Then you want to strip the .mp4 extension from the value of f, that is, strip the last 4 characters from the value of f, using ${f:0: -4} (this means “get a substring of f, starting at character 0 and ending at 5 characters before the end”).
You obviously want to terminate the loop with done. I also suggest wrapping the parameters in quotes, to prevent word splitting (that is, if the filenames contain certain characters, they might be split into multiple arguments to ffmpeg).
Putting it all together:
for f in *.mp4; do f=${f%.*}; ffmpeg -i "$f.mp4" -vf ass="$f.ass" "$f-output.mp4"; done
Of course, once you have run this, you need to get rid of all the output files before you can run it again. Or you can just put the output files in a different directory to begin with.
Edit: Another user posted an answer, which seems to have been deleted. It was a good answer but lacked explanation. It was basically the same as my answer, except that it used ${f%.mp4} to strip the .mp4 extension. My answer is probably slightly more complex but slightly more efficient, so it’s basically a matter of personal preference.
Edit 2: Based on the link provided by llogan’s comment, I have made these changes:
Remove the quotes in the assignment, as assignments are not subject to word splitting (this is also stated in the bash man page).
Use ${f%.*} to strip the extension. This strips a dot followed by any sequence of characters from the end. It looks for the shortest possible match, so it’s really looking for a dot followed by any sequence of non-dot characters at the end.
This question already has answers here:
Accessing bash command line args $# vs $*
(5 answers)
Closed 6 years ago.
x=('hello world' "HELLO")
Both ${#x[*]} and ${#x[#]} print the same output.
I understand the difference between $# and $* but I am interested to see the difference without command line arguments.
Always use # expansion unless you have reason to use *. # was added to work around a problem.
The two don't ALWAYS expand the same. The troubles involving* start with spaces and other shell metacharacters (quotes in particular, but $ and more as well).
The * leaves the metacharacters open for the shell to process them again, which is usually bad if you went out of your way to get them into the array. The # protects them by expanding each array element as if it was a separately quoted value, leaving all metacharacters intact.
I'm trying to implement the ls command with wildcard, *.
I have just learned the fact that most shells convert ls-argument containing * to the corresponding entries when performing ls command.
For example, The directory foo consist of a.file, b.file, and directory bar.
Then, the directory bar has c.file, d.file, and e.file.
and assume that current directory is the directory foo.
the argument */* is converted is to the following entries.
"bar/c.file", "bar/d.file", "bar/e.file"
How can program perform this? I don't know where to start from. And
there are many possible cases.
*/../*, ../../*, */*/*, etc.
Any advice would be awesome. Thank you..
You can of couse use glob() to do a lot of this work.
Such patterns are called globs, for some reason I won't dig up now. :)
POSIX provides glob(3) for programmatic wildcard path expansion.
I need to find out if a file or directory name contains any extension in Unix for a Bourne shell scripting.
The logic will be:
If there is a file extension
Remove the extension
And use the file name without the extension
This is my first question in SO so will be great to hear from someone.
The concept of an extension isn't as strictly well-defined as in traditional / toy DOS 8+3 filenames. If you want to find file names containing a dot where the dot is not the first character, try this.
case $filename in
[!.]*.*) filename=${filename%.*};;
esac
This will trim the extension (as per the above definition, starting from the last dot if there are several) from $filename if there is one, otherwise no nothing.
If you will not be processing files whose names might start with a dot, the case is superfluous, as the assignment will also not touch the value if there isn't a dot; but with this belt-and-suspenders example, you can easily pick the approach you prefer, in case you need to extend it, one way or another.
To also handle files where there is a dot, as long as it's not the first character (but it's okay if the first character is also a dot), try the pattern ?*.*.
The case expression in pattern ) commands ;; esac syntax may look weird or scary, but it's quite versatile, and well worth learning.
I would use a shell agnostic solution. Runing the name through:
cut -d . -f 1
will give you everything up to the first dot ('-d .' sets the delimeter and '-f 1' selects the first field). You can play with the params (try '--complement' to reverse selection) and get pretty much anything you want.
I'm implementing a linux shell for my weekend assignment and I am having some problems implementing wilcard matching as a feature in shell. As we all know, shells are a complete language by themselves, e.g. bash, ksh, etc. I don't need to implement the complete features like control structures, jobs etc. But how to implement the *?
A quick analysis gives you the following result:
echo *
lists all the files in the current directory. Is this the only logical manifestation of the shell? I mean, not considering the language-specific features of bash, is this what a shell does, internally? Replace a * with all the files in the current directory matching the pattern?
Also I have heard about Perl Compatible Regular Expression , but it seems to complex to use a third party library.
Any suggestions, links, etc.? I will try to look at the source code as well, for bash.
This is called "globbing" and the function performing this is named the same: glob(3)
Yes, that's what shell does. It will replace '*' characters by all files and folder names in cwd. It is in fact very basic regular expressions supporting only '?' and '*' and matching with file and folder names in cwd.
Remark that backslashed \* and '*' enclosed between simple or double quotes ' or " are not replaced (backslash and quotes are removed before passing to the command executed).
If you want more control than glob gives, the standard function fnmatch performs just glob matching.
Note that shells also performs word expansion (e.g. "~" → "/home/user"), which should be done before glob expansion, if you're doing filename matching manually. (Or use wordexp.)