Cannot shell out to find command - ruby

In Ruby, I want to shell out the following find command:
find . -type f -name '*.c' -exec mv {} . \;
I have tried many permutations of this command:
system("find . -type f -name '*.c' -exec mv {} . \;")
`find . -type f -name '*.c' -exec mv {} . \;`
%x(find . -type f -name '*.c' -exec mv {} . \;)
But when I run the command, find generates the error message:
find: -exec: no terminating ";" or "+"
I don't think the issue is characters which need to be escaped. This is probably a really simple fix, but any help would be greatly appreciated!


You need - as #mudasobwa indicated - actually pass the backslash to the find command. If you try your string in irb, you see immediately what's going wrong:
>> "find . -type f -name '*.c' -exec mv {} . \;"
=> "find . -type f -name '*.c' -exec mv {} . ;"
However, for actually running your find command, you need to make up your mind, whether system or %x() is the right tool to use. If you want do process the stdout of the command, you have to use %x, and in this case, you have to escape the backslash, because the string is then expended as if it were a string between double quotes:
find_stdout = %x(find . -type f -name '*.c' -exec mv {} . \\;)
If you are not interested in the result, but only in the overall success (exit code,....) of the command, you shhould use system, and in this case, you could use a single quoted string, which permits you to not escape the backslashes:
result = system('find . -type f -name "*.c" -exec mv {} . \;')
Of course, escaping here is not wrong either, and some people recommend for consistency and maintainability to always escape a backslash.

Related

Not able to replace all filenames in directory containing a substring with another substring

FROM=$1
TO=$2
find . -name '*'$FROM'*' -type f -exec bash -c 'mv "$1" "${1/$FROM/$TO}"' -- {} \;
find . -name '*'$FROM'*' -type f part is finding files correctly, but mv part doesn't seem to work

find exec and strip extension from filenames

Any idea why this command is not working? btw, I'm trying to strip out the extensions of all csv files in current directory.
find -type f -iname "*.csv" -exec mv {} $(basename {} ".csv") \;
Tried many variants including the parameter expansions, xargs ... Even then all went futile.

This should do:
find ./ -type f -iname "*.csv" -exec sh -c 'mv {} $(basename {} .csv)' \;
find is able to substitute {} with its findings since the quotes prevent executing the subshell until find is done. Then it executes the -exec part.
The problem why yours is not working is that $(basename {} ".csv") is executed in a subshell (-> $()) and evaluated beforehand. If we look at the command execution step-by-step you will see what happens:
find -type f -iname "*.csv" -exec mv {} $(basename {} ".csv") \; - your command
find -type f -iname "*.csv" -exec mv {} {} \; - subshell gets evaluated ($(basename {} ".csv") returns {} since it interprets {} as a literal)
find -type f -iname "*.csv" -exec mv {} {} \; - as you see now: move does actually nothing

First, take care that you have no subdirectories; find, without extra arguments, will automatically recur into any directory below.
Simple approach: if you have a small enough number of files, just use the glob (*) operator, and take advantage of rename:
$ rename 's/.csv$//' *.csv
If you have too many files, use find, and perhaps xargs:
$ find . -maxdepth 1 -type f -name "*.csv" | xargs rename 's/.csv$//'
If you want to be really safe, tell find and xargs to delimit with null-bytes, so that you don't have weird filenames (e.g., with spaces or newlines) mess up the process:
$ find . -maxdepth 1 -type f -name "*.csv" -print0 | xargs -0 rename 's/.csv$//'

Using + instead of \; in find -exec

I understand that using + rather than \; in a find command with -exec can speed things up because with \; the target of -exec is executed once for each result of the find command, whereas with + the target of -exec is executed "as needed."
This code works as expected and processes all subdirectories:
find "${directory}" -iname "*.jpg" -type d -prune -exec bash -c 'myscript "{}"' \;
But this code does NOT work:
find "${directory}" -iname "*.jpg" -type d -prune -exec bash -c 'myscript "$#"' bash {} +
It processes only one directory rather than all of them.
I'm obviously missing something about the proper syntax of using + when calling a function.

Performance difference in find command

Is there any performance difference in the below shell commands:
find . -type f -empty -exec rm '{}' \;
find . -type f -empty -exec sh -c "/bin/rm {}" \;

Your 2nd command is going to be slower since it will spawn a sub shell for each entry found by find command.
However at the same time 2nd command will be more flexible in nature if you want to do some variable assignment etc like this:
find . -type f -empty -exec sh -c "x=1; /bin/rm {}" \;

find . -exec echo {} \; = missing argument to `-exec'

Why doesn't this work? (echo is not the real command)
$ find . -type d -exec echo {} \;
find: missing argument to `-exec'
I managed to do that anyway like this:
$ for f in `find . -type d`; do echo $f; done

This work for me.
find . -type f -exec file '{}' \;
Braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation.

The following line is from the EXAMPLES section of man find:
find . -type f -exec file '{}' \;
It looks to me like the {} part needs to be in single quotes.

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