Use find command but exclude files in two directories

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刺人心
刺人心 2021-01-29 22:16

I want to find files that end with _peaks.bed, but exclude files in the tmp and scripts folders.

My command is like this:

6条回答
  •  醉梦人生
    2021-01-29 22:47

    Use

    find \( -path "./tmp" -o -path "./scripts" \) -prune -o  -name "*_peaks.bed" -print
    

    or

    find \( -path "./tmp" -o -path "./scripts" \) -prune -false -o  -name "*_peaks.bed"
    

    or

    find \( -path "./tmp" -path "./scripts" \) ! -prune -o  -name "*_peaks.bed"
    

    The order is important. It evaluates from left to right. Always begin with the path exclusion.

    Explanation

    Do not use -not (or !) to exclude whole directory. Use -prune. As explained in the manual:

    −prune    The primary shall always evaluate as  true;  it
              shall  cause  find  not  to descend the current
              pathname if it is a directory.  If  the  −depth
              primary  is specified, the −prune primary shall
              have no effect.
    

    and in the GNU find manual:

    -path pattern
                  [...]
                  To ignore  a  whole
                  directory  tree,  use  -prune rather than checking
                  every file in the tree.
    

    Indeed, if you use -not -path "./pathname", find will evaluate the expression for each node under "./pathname".

    find expressions are just condition evaluation.

    • \( \) - groups operation (you can use -path "./tmp" -prune -o -path "./scripts" -prune -o, but it is more verbose).
    • -path "./script" -prune - if -path returns true and is a directory, return true for that directory and do not descend into it.
    • -path "./script" ! -prune - it evaluates as (-path "./script") AND (! -prune). It revert the "always true" of prune to always false. It avoids printing "./script" as a match.
    • -path "./script" -prune -false - since -prune always returns true, you can follow it with -false to do the same than !.
    • -o - OR operator. If no operator is specified between two expressions, it defaults to AND operator.

    Hence, \( -path "./tmp" -o -path "./scripts" \) -prune -o -name "*_peaks.bed" -print is expanded to:

    [ (-path "./tmp" OR -path "./script") AND -prune ] OR ( -name "*_peaks.bed" AND print )
    

    The print is important here because without it is expanded to:

    { [ (-path "./tmp" OR -path "./script" )  AND -prune ]  OR (-name "*_peaks.bed" ) } AND print
    

    -print is added by find - that is why most of the time, you do not need to add it in you expression. And since -prune returns true, it will print "./script" and "./tmp".

    It is not necessary in the others because we switched -prune to always return false.

    Hint: You can use find -D opt expr 2>&1 1>/dev/null to see how it is optimized and expanded,
    find -D search expr 2>&1 1>/dev/null to see which path is checked.

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