Differences between version 17 and previous revision of BashOneLiners.
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| Newer page: | version 17 | Last edited on Saturday, December 4, 2004 12:23:43 am | by AristotlePagaltzis | Revert |
| Older page: | version 13 | Last edited on Friday, May 21, 2004 8:37:29 am | by AristotlePagaltzis | Revert |
@@ -1,44 +1,63 @@
!!! Sort a directory of mp3s into directories like Artist/Album Name/
-<verbatim>
+
<verbatim>
for file in *.mp3; do
eval $( id3tool "$file" | sed 's/^[^:]* //; s/:[\t ]*/="/; s/[[:cntrl:]]//g; /./!d; s/ *$/"/' )
{ [ "$Artist" -o "$Album" ] && dir="$Artist/$Album/" ; } || { [ "$Artist" ] && dir="$Artist/" ; } || continue
mkdir -p "$dir" ; mv "$file" "$dir/"
done
-</verbatim>
+
</verbatim>
It uses [id3tool | http://nekohako.xware.cx/id3tool/] to read the [ID3] tag, instructs [SED] to massage the information into something that looks like [Shell] script, executes that to put values into variables, checks which variables are set, and if at least an artist name (optionally also album name) is given, moves the file into that directory. (It's rather a mouthful for a oneliner, but hey.)
----
-!!! Refresh the all [GPG] keys from the [
KeyServer]
without flooding it:
+!!! Refresh the all [GPG] keys from the KeyServer without flooding it:
-<verbatim>
+
<verbatim>
for uid in $( gpg --with-colons --list-keys | grep ^pub | awk -F: '{print $5}' ) ; do gpg --refresh $uid ; sleep 5 ; done
-</verbatim>
+
</verbatim>
Alter the number after sleep(1) to change the speed of the refresh. This is equalivent to the slightly more understandable:
-<verbatim>
+
<verbatim>
for uid in $( gpg --with-colons --list-keys | grep ^pub | awk -F: '{print $5}' ) ; do
gpg --refresh $uid
sleep 5
done
-</verbatim>
+
</verbatim>
-! Notes by AristotlePagaltzis:
-This is a useless use of grep. Better written as follows
:
+__Notes by AristotlePagaltzis
:__
-<verbatim>
+This is a useless use of grep(1). Better written as follows:
+
+
<verbatim>
for uid in $( gpg --with-colons --list-keys | awk -F: '/^pub/{ print $5 }' ) ; do gpg --refresh $uid ; sleep 5 ; done
-</verbatim>
+
</verbatim>
-which can be abbreviated as
+Correcting self: this is still a useless use of backticks. As with most <tt>for f in $( ... )</tt> loops it is better written with a <tt>while</tt> loop:
-<verbatim>
+ <verbatim>
+ gpg --with-colons --list-keys | awk -F: '/^pub/{ print $5 }' | while read uid ; do gpg --refresh $uid ; sleep 5 ; done
+ </verbatim>
+
+''This applies to seq(1)-based loops too -- <tt>seq 1 10 | while read i</tt> is better than <tt>for i in $( seq 1 10 )</tt>.''
+
+This could be abbreviated as
+
+
<verbatim>
gpg --with-colons --list-keys | awk -F: '/^pub/{ print $5 }' | xargs -ri sh -c 'gpg --refresh {} ; sleep 5'
-</verbatim>
+
</verbatim>
+
+but since xargs(1) doesn't offer any speed controls itself, it requires an ugly roundabout via [Shell].
+
+----
+
+!!! Getting a random string
+
+From the ChoosingPasswords page (see that page for an explanation):
-It
's a pity xargs(1) doesn
't offer any speed controls itself, in that case the ugly roundabout via shell wouldn't be necessary.
+ <verbatim>
+ tr -dc
' -~
' < /dev/urandom | head -c 20
+ </verbatim>
