The $PATH is the reward

Other things that come to mind with $PATH and similar variables (like $LD_LIBRARY_PATH or $CLASSPATH):

• there may be multiple entries for the same part
• removing an entry from $PATH requires manual interaction
• '.' may end up in the middle of the path

The 'path' binary created by David Ingalls Bell solves all these issues, as can be seen from its project description on freshmeat.net:

path can be used to manipulate a colon-separated list
of paths contained in an environment variable such as
PATH. New paths can be added either to the beginning or
the end of the path list, paths can be removed from the
path list, and several checks can be made on the paths
contained in the path list. All duplicate paths in the
list are removed.
( http://freshmeat.net/projects/path/ )

There is only one issue left: 'path' can modify existing $PATH variable contents just fine but it can't modify the environment of your current shell.

So i have created a set of bash functions wrapping 'path' a long time ago that i now want to share. The functions i created are named 'pathadd', 'pathfront', 'pathdel' etc.

Lets have a look at one of these first:

  # prepend directory to path if not already present
  # "pathadd dir" -> prepend to $PATH
  # "pathadd MY_PATH dir" -> prepend to $MY_PATH
  function pathfront()
  { 
    if [ $# = 2 ] 
    then 
      export $1=`path -var $1 -rb $2`;
    else
      export PATH=`path -var PATH -rb $1`; 
    fi 
  }

'pathfront' will add a directory to the beginning of $PATH or another specified variable. If the directory was already included in the path it is moved to the front, no duplicates are created. If '.' is part of the path it will always be the first ement of the path, the given directory wil becomenumber 2 in the list then.

Examples:

  # if called with one argument the variable defaults to $PATH
  pathadd /usr/local/mysql/bin  

  # when called with two arguments the first is a varaible name
  pathadd LD_LIBRARY_PATH /usr/local/mysql/lib/mysql

So if i want to test things with a specific mysql version installed on my box i do this first:

  pathfront /usr/local/mysql-x.y.z/bin
  pathfront /usr/local/mysql-x.y.z/libexec
  pathfront LD_LIBRARY /usr/local/mysql-x.y.z/lib/mysql

and after i'm done i'll run the reverse to clean up the pathes:

  pathdel /usr/local/mysql-x.y.z/bin
  pathdel /usr/local/mysql-x.y.z/libexec
  pathdel LD_LIBRARY /usr/local/mysql-x.y.z/lib/mysql

A full list of bash wrapper functions for path incldues:

path_add

add entry to end of path if it doesn't already exists, else leave path as is

path_back

add entry to end of path, if it already exits then move it to the end instead

path_front

add entry to front of part or move it there if it already exists, but make sure '.' is always the first element if it is part of the path

path_del

remove entry from the path

path_list

show current path elements line by line

path_clean

clean up duplicate entries and remove entries pointing to nonexisting locations

pach_check

check current path and report possible problems

• path project page
• pathtools.sh