Bash – * at end of directory path

bashdirectorypathscripting

I have a question about the * character at the end of a directory path in a bash script.

I have a script that's supposed to automatically delete some archives from a server once they get old enough. The script is on machine A and I need to run it on machine B. I access both machines remotely through ssh (no sudo, just regular user). One of the rules of the script is that it needs to only delete archives in the folders beginning with dirA/dirB/dirC/dirD/dirE*.

However, there is no dirE in that location so I'm guessing the * stands for some variable. This is what I'd like to know, what does the * mean at the end of the directory path and what does it make the script do?

Best Answer

The * here is a "globbing character" and means "match 0 or more characters". To illustrate, consider this directory:

$ ls
dirA  dire  dirE  dirEa  dirEEE
$ echo dirE*
dirE dirEa dirEEE

As you can see above, the glob dirE* matches dirE, dirEa and dirEEE but not dirA or dire (*nix systems are case sensitive).

So, in your script, that means it will delete archives from any directory in dirA/dirB/dirC/dirD/ whose name begins with dirE.

Related Solutions

Directory Filenames – Path Syntax Rules

There are three types of paths:

relative paths like foo, foo/bar, ../a, .. They don't start with / and are relative to the current directory of the process making a system call with that path.
absolute paths like /, /foo/bar or ///x. They start with 1, or 3 or more /, they are not relative, are looked up starting from the / root directory.
POSIX allows //foo to be treated specially, but doesn't specify how. Some systems use that for special cases like network files. It has to be exactly 2 slashes.

Other than at the start, sequences of slashes act like one.

~ is only special to the shell, it's expanded by the shell, it's not special to the system at all. How it's expanded is shell dependent. Shells do other forms of expansions like globbing (*.txt) or variable expansion /$foo/$bar or others. As far as the system is concerned ~foo is just a relative path like _foo or foo.

Things to bear in mind:

foo/ is not the same as foo. It's closer to foo/. than foo (especially if foo is a symlink) for most system calls on most systems (foo// is the same as foo/ though).
a/b/../c is not necessarily the same as a/c (for instance if a/b is a symlink). Best is not to treat .. specially.
it's generally safe to consider a/././././b the same as a/b though.

Bash – Defining the start and end point of a loop in bash

#!/bin/bash
a=1
b=1

cd ~/PATH/
for i in $(ls -v) ;do
  (cd $i/ && action) && echo "completed" || echo "error"
  a=$((a+b)); [ "$a" -gt 50 ] && break 
  echo "Next Folder"
done

Best Answer

Related Solutions

Directory Filenames – Path Syntax Rules

Bash – Defining the start and end point of a loop in bash

Related Question