My goal is to empty every file in a directory. I DON'T want to actually delete the file, I just want to delete it's contents.
If you want to do this with a single file you can do > file.txt
If I want to run this operation on every file in a directory I can do this:
find . -exec /bin/bash -c '> {}' \;
Notice how the above command has to call /bin/bash. This is because simply running the command like this, find . -exec > {} \; says find: invalid argument ;' to -exec' I suspect this is because the redirection symbol is confusing the command.
I would like to run this command without needing to run /bin/bash within -exec
How can this be done?
One easy way to do this is by using truncate:
find -type f -exec truncate -s0 {} +
If you want to only use bash, you could use a while loop:
find -type f -print0 |
while IFS= read -r -d '' file; do
> "$file"
done
Finally, if you didn't mind using bash -c, it would be better to do it as follows to avoid calling bash so many times:
find -type f -exec bash -c 'for file; do > "$file"; done' - {} +
although I don't like that solution.
Related
This question already has answers here:
Recursively change file extensions in Bash
(6 answers)
Closed 6 years ago.
The user inputs a file type they are looking for; it is stored in $arg1; the file type they would like to change them is stored as $arg2. I'm able to find what I'm looking for, but I'm unsure of how to keep the filename the same but just change the type... ie., file1.txt into file1.log.
find . -type f -iname "*.$arg1" -exec mv {} \;
To enable the full power of shell parameter expansions, you can call bash -c in your exec action:
find . -type f -iname "*.$arg1" \
-exec bash -c 'echo mv "$1" "${1/%.*/$1}"' _ {} "$arg2" \;
We add {} and "$arg2" as a parameters to bash -c, so they become accessible within the command as $0 and $1. ${0%.*} removes the extension, to be replaced by whatever $arg2 expands to.
As it is, the command just prints the mv commands it would execute; to actually rename the files, the echo has to be removed.
The quoting is relevant: the argument to bash -c is in single quotes to prevent $0 and $1 from being expanded prematurely, and the two arguments to mv, and arg2 are also quoted to deal with file names with spaces in them.
Combining the find -exec bash idea with the bash loop idea, you can use the + terminator on the -exec to tell find to pass multiple filenames to a single invocation of the bash command. Pass the new type as the first argument - which shows up in $0 and so is conveniently skipped by a for loop over the rest of the command-line arguments - and you have a pretty efficient solution:
find . -type f -iname "*.$arg1" -exec bash -c \
'for arg; do mv "$arg" "${arg%.*}.$0"; done' "$arg2" {} +
Alternatively, if you have either version of the Linux rename command, you can use that. The Perl one (a.k.a. prename, installed by default on Ubuntu and other Debian-based distributions; also available for OS X from Homebrew via brew install rename) can be used like this:
find . -type f -iname "*.$arg1" -exec rename 's/\Q'"$arg1"'\E$/'"$arg2"'/' {} +
That looks a bit ugly, but it's really just the s/old/new/ substitution command familiar from many UNIX tools. The \Q and \E around $arg1 keep any weird characters inside the suffix from being interpreted as regular expression metacharacters that might match something unexpected; the $ after the \E makes sure the pattern only matches at the end of the filename.
The pattern-based version installed by default on Red Hat-based Linux distros (Fedora, CentOS, etc) is simpler:
find . -type f -iname "*.$arg1" -exec rename ".$arg1" ".$arg2" {} +
but it's also dumber: if you rename .com .exe stackoverflow.com_scanner.com, you'll get a file named stackoverflow.exe_scanner.exe.
I would do it like so:
find . -type f -iname "*.$arg1" -print0 |\
while IFS= read -r -d '' file; do
mv -- "$file" "${file%$arg1}$arg2"
done
I took your find command and fed its output to a while loop. Within that loop, I am doing the actual renaming. This way I have the name of the file as a variable that I can manipulate using bash's string manipulation operations.
If you have perl based rename command
Sample directory:
$ find
.
./a"bn.txt
./t2.abc
./abc
./abc/t1.txt
./abc/list.txt
./a bc.txt
Sample args:
$ arg1='txt'
$ arg2='log'
Dry run:
$ find -type f -iname "*.$arg1" -exec rename -n "s/$arg1$/$arg2/" {} +
rename(./a"bn.txt, ./a"bn.log)
rename(./abc/t1.txt, ./abc/t1.log)
rename(./abc/list.txt, ./abc/list.log)
rename(./a bc.txt, ./a bc.log)
Remove -n option once it is okay:
$ find -type f -iname "*.$arg1" -exec rename "s/$arg1$/$arg2/" {} +
$ find
.
./a bc.log
./t2.abc
./abc
./abc/list.log
./abc/t1.log
./a"bn.log
I was helped out today with a command, but it doesn't seem to be working. This is the command:
find /home/me/download/ -type f -name "*.rm" -exec ffmpeg -i {} -sameq {}.mp3 && rm {}\;
The shell returns
find: missing argument to `-exec'
What I am basically trying to do is go through a directory recursively (if it has other directories) and run the ffmpeg command on the .rm file types and convert them to .mp3 file types. Once this is done, remove the .rm file that has just been converted.
A -exec command must be terminated with a ; (so you usually need to type \; or ';' to avoid interpretion by the shell) or a +. The difference is that with ;, the command is called once per file, with +, it is called just as few times as possible (usually once, but there is a maximum length for a command line, so it might be split up) with all filenames. See this example:
$ cat /tmp/echoargs
#!/bin/sh
echo $1 - $2 - $3
$ find /tmp/foo -exec /tmp/echoargs {} \;
/tmp/foo - -
/tmp/foo/one - -
/tmp/foo/two - -
$ find /tmp/foo -exec /tmp/echoargs {} +
/tmp/foo - /tmp/foo/one - /tmp/foo/two
Your command has two errors:
First, you use {};, but the ; must be a parameter of its own.
Second, the command ends at the &&. You specified “run find, and if that was successful, remove the file named {};.“. If you want to use shell stuff in the -exec command, you need to explicitly run it in a shell, such as -exec sh -c 'ffmpeg ... && rm'.
However you should not add the {} inside the bash command, it will produce problems when there are special characters. Instead, you can pass additional parameters to the shell after -c command_string (see man sh):
$ ls
$(echo damn.)
$ find * -exec sh -c 'echo "{}"' \;
damn.
$ find * -exec sh -c 'echo "$1"' - {} \;
$(echo damn.)
You see the $ thing is evaluated by the shell in the first example. Imagine there was a file called $(rm -rf /) :-)
(Side note: The - is not needed, but the first variable after the command is assigned to the variable $0, which is a special variable normally containing the name of the program being run and setting that to a parameter is a little unclean, though it won't cause any harm here probably, so we set that to just - and start with $1.)
So your command could be something like
find -exec bash -c 'ffmpeg -i "$1" -sameq "$1".mp3 && rm "$1".mp3' - {} \;
But there is a better way. find supports and and or, so you may do stuff like find -name foo -or -name bar. But that also works with -exec, which evaluates to true if the command exits successfully, and to false if not. See this example:
$ ls
false true
$ find * -exec {} \; -and -print
true
It only runs the print if the command was successfully, which it did for true but not for false.
So you can use two exec statements chained with an -and, and it will only execute the latter if the former was run successfully.
Try putting a space before each \;
Works:
find . -name "*.log" -exec echo {} \;
Doesn't Work:
find . -name "*.log" -exec echo {}\;
I figured it out now. When you need to run two commands in exec in a find you need to actually have two separate execs. This finally worked for me.
find . -type f -name "*.rm" -exec ffmpeg -i {} -sameq {}.mp3 \; -exec rm {} \;
You have to put a space between {} and \;
So the command will be like:
find /home/me/download/ -type f -name "*.rm" -exec ffmpeg -i {} -sameq {}.mp3 && rm {} \;
Just for your information:
I have just tried using "find -exec" command on a Cygwin system (UNIX emulated on Windows), and there it seems that the backslash before the semicolon must be removed:
find ./ -name "blabla" -exec wc -l {} ;
For anyone else having issues when using GNU find binary in a Windows command prompt. The semicolon needs to be escaped with ^
find.exe . -name "*.rm" -exec ffmpeg -i {} -sameq {}.mp3 ^;
You need to do some escaping I think.
find /home/me/download/ -type f -name "*.rm" -exec ffmpeg -i {} \-sameq {}.mp3 \&\& rm {}\;
Just in case anyone sees a similar "missing -exec args" in Amazon Opsworks Chef bash scripts, I needed to add another backslash to escape the \;
bash 'remove_wars' do
user 'ubuntu'
cwd '/'
code <<-EOH
find /home/ubuntu/wars -type f -name "*.war" -exec rm {} \\;
EOH
ignore_failure true
end
Also, if anyone else has the "find: missing argument to -exec" this might help:
In some shells you don't need to do the escaping, i.e. you don't need the "\" in front of the ";".
find <file path> -name "myFile.*" -exec rm - f {} ;
Both {} and && will cause problems due to being expanded by the command line. I would suggest trying:
find /home/me/download/ -type f -name "*.rm" -exec ffmpeg -i \{} -sameq \{}.mp3 \; -exec rm \{} \;
In my case I needed to execute "methods" from by bash script, which does not work when using -exec bash -c, so I add another solution I found here, as well:
UploadFile() {
curl ... -F "file=$1"
}
find . | while read file;
do
UploadFile "$file"
done
This thread pops up first when searching for solutions to execute commands for each file from find, so I hope it's okay that this solution does not use the -exec argument
I got the same error when I left a blank space after the ending ; of an -exec command.So, remove blank space after ;
If you are still getting "find: missing argument to -exec" try wrapping the execute argument in quotes.
find <file path> -type f -exec "chmod 664 {} \;"
I have the code below
find . -type f -exec sed -i 's#<![endif]>##g' {} +
find . -type f -exec sed -i 's#<script src="/js/vendor/modernizr-2.6.2.min.js?v=201425100529"></script>##g' {} +
find . -type f -exec sed -i 's# <!--[if lt IE 9]>##g' {} +
in a bash file.
If I run the lines directly in terminal it works, but If I run them together in a sh file I have an error:
find: missing argument to '-exec'
The reason the command execution succeeds but the script failed is,
when the script gets executed the find command searches for all files and directories in the current execution path ( as . is used in find). Again this also includes the script itself. This creates the script to be overwritten/modified by the sed.
And so instead of keeping the script in the same directory when the file edits needs to be done, the script can be kept in some other directory and an absolute path can be give to the find command.
And it is also recommended to terminate commands with \; to indicate the end of arguments.
Always use bash to execute scripts instead of sh which means bourne shell . Generally bash will be a symlink for sh but it will run in a compatibility mode which causes bash to loose modern functions.
#!/bin/bash
find /Absolute/path -type f -exec sed -i 's#<!\[endif\]>##g' '{}' \;
find /Absolute/path -type f -exec sed -i 's#<script src="/js/vendor/modernizr-2.6.2.min.js?v=201425100529"></script>##g' '{}' \;
find /Absolute/path -type f -exec sed -i 's# <!--\[if lt IE 9\]>##g' '{}' \;
I have one script that only writes data to stdout. I need to run it for multiple files and generate a different output file for each input file and I was wondering how to use find -exec for that. So I basically tried several variants of this (I replaced the script by cat just for testability purposes):
find * -type f -exec cat "{}" > "{}.stdout" \;
but could not make it work since all the data was being written to a file literally named{}.stdout.
Eventually, I could make it work with :
find * -type f -exec sh -c "cat {} > {}.stdout" \;
But while this latest form works well with cat, my script requires environment variables loaded through several initialization scripts, thus I end up with:
find * -type f -exec sh -c "initscript1; initscript2; ...; myscript {} > {}.stdout" \;
Which seems a waste because I have everything already initialized in my current shell.
Is there a better way of doing this with find? Other one-liners are welcome.
You can do it with eval. It may be ugly, but so is having to make a shell script for this. Plus, it's all on one line.
For example
find -type f -exec bash -c "eval md5sum {} > {}.sum " \;
A simple solution would be to put a wrapper around your script:
#!/bin/sh
myscript "$1" > "$1.stdout"
Call it myscript2 and invoke it with find:
find . -type f -exec myscript2 {} \;
Note that although most implementations of find allow you to do what you have done, technically the behavior of find is unspecified if you use {} more than once in the argument list of -exec.
If you export your environment variables, they'll already be present in the child shell (If you use bash -c instead of sh -c, and your parent shell is itself bash, then you can also export functions in the parent shell and have them usable in the child; see export -f).
Moreover, by using -exec ... {} +, you can limit the number of shells to the smallest possible number needed to pass all arguments on the command line:
set -a # turn on automatic export of all variables
source initscript1
source initscript2
# pass as many filenames as possible to each sh -c, iterating over them directly
find * -name '*.stdout' -prune -o -type f \
-exec sh -c 'for arg; do myscript "$arg" > "${arg}.stdout"' _ {} +
Alternately, you can just perform the execution in your current shell directly:
while IFS= read -r -d '' filename; do
myscript "$filename" >"${filename}.out"
done < <(find * -name '*.stdout' -prune -o -type f -print0)
See UsingFind discussing safely and correctly performing bulk actions through find; and BashFAQ #24 discussing the use of process substitution (the <(...) syntax) to ensure that operations are performed in the parent shell.
I'm trying to run the expand shell command on all files found by a find command. I've tried -exec and xargs but both failed. Can anyone explain me why? I'm on a mac for the record.
find . -name "*.php" -exec expand -t 4 {} > {} \;
This just creates a file {} with all the output instead of overwriting each individual found file itself.
find . -name "*.php" -print0 | xargs -0 -I expand -t 4 {} > {}
And this just outputs
4 {}
xargs: 4: No such file or directory
Your command does not work for two reasons.
The output redirection is done by the shell and not by find. That means that the shell will redirect finds output into the file {}.
The redirection would occur immediately. That means that the file will be written even before it is read by the expand command. So it's not possible to redirect a command's output into the input file.
Unfortunately expand doesn't allow to write it's output into a file. So you have to use output redirection. If you use bash you could define a function that executes expand, redirects the output into a temporary file and move the temporary file back over the original file. The problem is that find will run a new shell to execute the expand command.
But there is a solution:
expand_func () {
expand -t 4 "$1" > "$1.tmp"
mv "$1.tmp" "$1"
}
export -f expand_func
find . -name \*.php -exec bash -c 'expand_func {}' \;
You are exporting the function expand_func to sub shells using export -f. And you don't execute expand itself using find -exec but you execute a new bash that executes the exported expand_func.
'expand' isn't really worth the trouble.
You can just use sed instead:
find . -name "*.php" | xargs sed -i -e 's/\t/ /g'