I would like to rename several files picked by find in some directory, then use xargs and mv to rename the files, with parameter expansion. However, it did not work...
example:
mkdir test
touch abc.txt
touch def.txt
find . -type f -print0 | \
xargs -I {} -n 1 -0 mv {} "${{}/.txt/.tx}"
Result:
bad substitution
[1] 134 broken pipe find . -type f -print0
Working Solution:
for i in ./*.txt ; do mv "$i" "${i/.txt/.tx}" ; done
Although I finally got a way to fix the problem, I still want to know why the first find + xargs way doesn't work, since I don't think the second way is very general for similar tasks.
Thanks!
Remember that shell variable substitution happens before your command runs. So when you run:
find . -type f -print0 | \
xargs -I {} -n 1 -0 mv {} "${{}/.txt/.tx}"
The shell tries to expan that ${...} construct before xargs even
runs...and since that contents of that expression aren't a valid shell variable reference, you get an error. A better solution would be to use the rename command:
find . -type f -print0 | \
xargs -I {} -0 rename .txt .tx {}
And since rename can operate on multiple files, you can simplify
that to:
find . -type f -print0 | \
xargs -0 rename .txt .tx
Related
I want to run a loop over all files of a particular extension in a directory:
for i in *.bam
do
...
done
However, if the command that I run inside the loop creates a temporary file of the same extension, the loop tries to process this new tmp file as well. This is unwanted. So, I thought the following would solve the problem: first list all the *.bam files in the directory, save that list to a variable, and then loop over this saved list:
list_bam=$(for i in *.bam; do echo $i; done)
for i in $list_bam
do
...
done
To my surprise, this runs into the same problem! Could someone please explain the logic behind this and how to fix it so that the loop only processes the pre-existing .bam files?
Instead of a loop you can use find and xargs
find . -maxdepth 1 -type f -name "*.bam" -print0 | \
xargs -0 -I{} bash -c 'echo "{}" > "{}.new.bam"'
or
find . -maxdepth 1 -type f -name "*.bam" -print0 | \
xargs -0 -I{} bash -c 'echo "$1" > "$1.new.bam"' -- {}
example:
$ touch a.bam b.bam
$ ls
a.bam b.bam
$ find . -maxdepth 1 -type f -name "*.bam" -print0 | \
xargs -0 -I{} bash -c 'echo "{}" > "{}.new.bam"'
$ ls
a.bam a.bam.new.bam b.bam b.bam.new.bam
You should perhaps make sure that your globbing expression *.bam couldn't be interpreted afterward with something like:
list_bam=$(ls *.bam)
...
...but, as noticed by #glenn in the comments, this is a bad idea.
Something similar should be made using a find ... -print0 | xargs -0 ... command template.
I would like to recursively go through all subdirectories and remove the oldest two PDFs in each subfolder named "bak":
Works:
find . -type d -name "bak" \
-exec bash -c "cd '{}' && pwd" \;
Does not work, as the double quotes are already in use:
find . -type d -name "bak" \
-exec bash -c "cd '{}' && rm "$(ls -t *.pdf | tail -2)"" \;
Any solution to the double quote conundrum?
In a double quoted string you can use backslashes to escape other double quotes, e.g.
find ... "rm \"\$(...)\""
If that is too convoluted use variables:
cmd='$(...)'
find ... "rm $cmd"
However, I think your find -exec has more problems than that.
Using {} inside the command string "cd '{}' ..." is risky. If there is a ' inside the file name things will break and might execcute unexpected commands.
$() will be expanded by bash before find even runs. So ls -t *.pdf | tail -2 will only be executed once in the top directory . instead of once for each found directory. rm will (try to) delete the same file for each found directory.
rm "$(ls -t *.pdf | tail -2)" will not work if ls lists more than one file. Because of the quotes both files would be listed in one argument. Therefore, rm would try to delete one file with the name first.pdf\nsecond.pdf.
I'd suggest
cmd='cd "$1" && ls -t *.pdf | tail -n2 | sed "s/./\\\\&/g" | xargs rm'
find . -type d -name bak -exec bash -c "$cmd" -- {} \;
You have a more fundamental problem; because you are using the weaker double quotes around the entire script, the $(...) command substitution will be interpreted by the shell which parses the find command, not by the bash shell you are starting, which will only receive a static string containing the result from the command substitution.
If you switch to single quotes around the script, you get most of it right; but that would still fail if the file name you find contains a double quote (just like your attempt would fail for file names with single quotes). The proper fix is to pass the matching files as command-line arguments to the bash subprocess.
But a better fix still is to use -execdir so that you don't have to pass the directory name to the subshell at all:
find . -type d -name "bak" \
-execdir bash -c 'ls -t *.pdf | tail -2 | xargs -r rm' \;
This could stll fail in funny ways because you are parsing ls which is inherently buggy.
You are explicitely asking for find -exec. Usually I would just concatenate find -exec find -delete but in your case only two files should be deleted. Therefore the only method is running subshell. Socowi already gave nice solution, however if your file names do not contain tabulator or newlines, another workaround is find while read loop.
This will sort files by mtime
find . -type d -iname 'bak' | \
while read -r dir;
do
find "$dir" -maxdepth 1 -type f -iname '*.pdf' -printf "%T+\t%p\n" | \
sort | head -n2 | \
cut -f2- | \
while read -r file;
do
rm "$file";
done;
done;
The above find while read loop as "one-liner"
find . -type d -iname 'bak' | while read -r dir; do find "$dir" -maxdepth 1 -type f -iname '*.pdf' -printf "%T+\t%p\n" | sort | head -n2 | cut -f2- | while read -r file; do rm "$file"; done; done;
find while read loop can also handle NUL terminated file names. However head can not handle this, so I did improve other answers and made it work with nontrivial file names (only GNU + bash)
replace 'realpath' with rm
#!/bin/bash
rm_old () {
find "$1" -maxdepth 1 -type f -iname \*.$2 -printf "%T+\t%p\0" | sort -z | sed -zn 's,\S*\t\(.*\),\1,p' | grep -zim$3 \.$2$ | xargs -0r realpath
}
export -f rm_old
find -type d -iname bak -execdir bash -c 'rm_old "{}" pdf 2' \;
However bash -c might still exploitable, to make it more secure let stat %N do the quoting
#!/bin/bash
rm_old () {
local dir="$1"
# we don't like eval
# eval "dir=$dir"
# this works like eval
dir="${dir#?}"
dir="${dir%?}"
dir="${dir//"'$'\t''"/$'\011'}"
dir="${dir//"'$'\n''"/$'\012'}"
dir="${dir//$'\047'\\$'\047'$'\047'/$'\047'}"
find "$dir" -maxdepth 1 -type f -iname \*.$2 -printf '%T+\t%p\0' | sort -z | sed -zn 's,\S*\t\(.*\),\1,p' | grep -zim$3 \.$2$ | xargs -0r realpath
}
find -type d -iname bak -exec stat -c'%N' {} + | while read -r dir; do rm_old "$dir" pdf 2; done
I want to find a file, and simultaneously copy it to another directory like this:
cp (find . -name myFile | tail -n 1) dir/to/copy/to
But this says unexpected token `find'
Is there a better way to do this?
You may use a pipeline:
find . -name 'myFile' -print0 | tail -z -n 1 | xargs -0 -I {} cp {} /dir/to/copy/to/
Using -print0 option to address filenames with whitespace, glob characters
find . -name 'myFile' -print0 | tail -n 1 | xargs -0 -I {} cp {} /dir/to/copy/to/
Two options are available-
Appended the missing $() - to evaluate command (not sure the purpose of tail command, only required for samefile in multiple directories)
cp $(find . -name myFile | tail -n 1) dir/to/copy/to
find . -name myFile -type f -exec cp {} dir/to/copy/to \;
I am currently in data folder which has following files and folders
Folders:
ISOLATE
JUKEBOX
Files:
XXX-12-2345-67A-89T-1011-12.ab20.RenderBase20.ISOLATE.quantifier.txt
XXX-12-2345-67A-89T-1011-12.ab20.RenderBase20.JUKEBOX.quantifier.txt
XXX-24-2345-67A-89T-2022-24.ab10.RenderBase20.ISOLATE.quantifier.txt
XXX-24-2345-67A-89T-2022-24.ab10.RenderBase20.JUKEBOX.quantifier.txt
...
I want to put the files with .ISOLATE in Folder ISOLATE and .JUKEBOX ones in the JUKEBOX folder. How could I perform this task using terminal?
There are more than 12000 files, so I cannot really change the naming scheme.
Thanks in advance
Try to use wildcards:
mv *.ISOLATE.quantifier.txt ISOLATE/
mv *.JUKEBOX.quantifier.txt JUKEBOX/
If the number of files is too high, you might need to move them in smaller loads.
find -name '*.ISOLATE.quantifier.txt' -maxdepth 1 -exec mv {} ISOLATE/ +
-exec with + should accumulate the command line arguments the same way as xargs, so you shouldn't overflow the maximal number of arguments.
Since you're dealing with huge # of files, you can use this mv with xargs:
printf '%s\0' *.ISOLATE.* | xargs -0 mv -t ISOLATE/
printf '%s\0' *.JUKEBOX.* | xargs -0 mv -t JUKEBOX/
In addition to trying wildcards (bash pattern match or globs), which at some point will hit an upper limit based on the number of files, you can also use find and xargs:
find . -name '*.ISOLATE.*.txt' -maxdepth 1 -print0 | xargs -0 -IFILE mv FILE ./ISOLATE
find . -name '*.JUKEBOX.*.txt' -maxdepth 1 -print0 | xargs -0 -IFILE mv FILE ./JUKEBOX
Doing this won't be subject to the maximum number of command line arguments that the glob solution may hit.
They key things in the commands above are:
-maxdepth 1 ensures that find won't keep looking into the ./ISOLOATE or ./JUKEBOX subdirectories
-print0 causes find to delimit the file names with a null byte rather than whitespace. This protects you against files that have spaces or other special characters in their names.
-0 causes xargs to use the null byte delimiter rather than whitespace for the same reason
-IFILE tells xargs to use the string FILE for each of the arguments. Typically xargs puts the filenames on the right, which wouldn't work with the mv command.
I tested the approach with a small shell script:
touch XXX-12-2345-67A-89T-1011-12.ab20.RenderBase20.ISOLATE.quantifier.txt
touch XXX-12-2345-67A-89T-1011-12.ab20.RenderBase20.JUKEBOX.quantifier.txt
touch XXX-24-2345-67A-89T-2022-24.ab10.RenderBase20.ISOLATE.quantifier.txt
touch XXX-24-2345-67A-89T-2022-24.ab10.RenderBase20.JUKEBOX.quantifier.txt
mkdir ISOLATE
mkdir JUKEBOX
find . -name '*.ISOLATE.*.txt' -maxdepth 1 -print0 | xargs -0 -IFILE mv FILE ./ISOLATE
find . -name '*.JUKEBOX.*.txt' -maxdepth 1 -print0 | xargs -0 -IFILE mv FILE ./JUKEBOX
find .
Which outputs:
$ bash example.sh
.
./example.sh
./ISOLATE
./ISOLATE/XXX-12-2345-67A-89T-1011-12.ab20.RenderBase20.ISOLATE.quantifier.txt
./ISOLATE/XXX-24-2345-67A-89T-2022-24.ab10.RenderBase20.ISOLATE.quantifier.txt
./JUKEBOX
./JUKEBOX/XXX-12-2345-67A-89T-1011-12.ab20.RenderBase20.JUKEBOX.quantifier.txt
./JUKEBOX/XXX-24-2345-67A-89T-2022-24.ab10.RenderBase20.JUKEBOX.quantifier.txt
I'm getting results using find with filenames that have '~' and .swp, etc. So I did the following, but is there a better way to do this? The '.*.js' -iname '*.js' part feels "redundant".
$ find ./ '.*.js' -iname '*.js' -print0 | xargs -0 grep -n ".*loginError.*"
find: `.*.js': No such file or directory
./js/signin.js:252: foo.loginError();
./js/signin.js:339:foo.loginError = function() {
./js/signin.js:340: foo.log("ui.loginError");
Try using
find . -name \*.js -print0 | xargs -0 grep -n ".*loginError.*"
That will find only files with 'js' extension and not ending in ~ or .swp
EDIT: Added '0' -print0 (edit requires 6 characters so I'm adding this; ergh!)
To do it all in one command without the xargs you could do it like this
find . -name "*.js" -exec grep -n ".*loginError.*" /dev/null {} \;
the /dev/null piece is to make grep think it's searching multiple files and then it'll output the filename correctly, otherwise it'd just print out the line number without telling you which file it's in