Remove first directory components from path of file

bash shell text-processing
Libor Zapletal picture Libor Zapletal · Mar 15, 2011 · Viewed 40k times · Source

I need to remove one directory (the leftmost) from variables in Bash. I found ways how can I remove all the path or use dirname and others but it was removing all or one path component on the right side; it wouldn't help me. So you have a better understanding of what I need, I'll write an example:

I have a/project/hello.c, a/project/docs/README, ... and I want to remove that a/ so after some commands I´ll have project/hello.c and project/docs/README, ...

Answer

Jonathan Leffler picture Jonathan Leffler · Mar 15, 2011

You can use any of:

x=a/b/c/d
y=a/
echo ${x#a/}
echo ${x#$y}
echo ${x#*/}

All three echo commands produce b/c/d; you could use the value in any way you choose, of course.

The first is appropriate when you know the name you need to remove when writing the script.

The second is appropriate when you have a variable that contains the prefix you need to remove (minor variant: y=a; echo ${x#$y/}).

The third is the most general - it removes any arbitrary prefix up to the first slash. I was pleasantly surprised to find that the * worked non-greedily when I tested it with bash (version 3.2) on MacOS X 10.6.6 - I'll put that down to too much Perl and regex work (because, when I think about it, * in shell doesn't include slashes).

Related questions

Select random lines from a file

In a Bash script, I want to pick out N random lines from input file and output to another file. How can this be done?

Read More
shell replace cr\lf by comma

I have input.txt 1 2 3 4 5 I need to get such output.txt 1,2,3,4,5 How to do it?

Read More
How to concatenate string variables in Bash

In PHP, strings are concatenated together as follows: $foo = "Hello"; $foo .= " World"; Here, $foo becomes "Hello World". How is this accomplished in Bash?

Read More