I want to find files that end with _peaks.bed
, but exclude files in the tmp
and scripts
folders.
My command is like this:
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.
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.