Sstrhsrtj

I need to prepend directories to the path variable in my .cshrc file and I want to make sure that the entries are not repeated when compared to existing directories in the path variable. Can someone advise suitable commands for that? The path on my machine is : separated, not space separated.

If on Linux, I suppose your csh is tcsh. Then you should be able to do:

set -f path=("/new/entry" $path:q)

In csh, tcsh and zsh, the $path special array variable is tied to the $PATH scalar environment variable in that the elements of the $path array are constructed by splitting the $PATH variable on the colon character. Any modification of either $path or $PATH is automatically reflected into the other variable.

-f above is to retain only the first entry. $path:q is the elements of $path, quoted, that is preventing word splitting. So the syntax above prepends the /new/entry or moves it to the front if it was already there.

Why would you be using csh though?

Note: the quotes above are necessary. Or more precisely, all the characters in /new/entry need to be quoted one way or another.

set -f path=('/new/'e"ntry" $path:q)

is OK.

set -f path=(/'new/entry' $path:q)

is not. You can always do it in two stages though:

set path=(/new/entry $path:q)

set -f path=($path:q)

^{(one of the reasons you may want to stay away from csh)}

I believe that the following can do what you want.

if ( $PATH =~ */some/path* ) then

    set PATH = ($PATH:/some/path)

endif

^{Note: I'm more of a bash user, so if I have a small error let me know
csh if test}

(note: i can not test the below right now... hope it works)

I just add this as a complement to stephane answer: how to get rid of duplicates in $PATH

I'll assume you have

• directories that should stay in front


• and other directories as well, order not important (ie, placed AFTER the above)

so:

To un-duplicate entries:

UNIQUE_LIST=$( echo "$PATH" | tr ':' 'n' | sort | uniq)



# then we place in front those from UNIQUELIST that match an ordered list

# note that that way, those who didn't have "/sbin" still won't have it, but if they did

# it will be at the right place in the list

shouldbefirst="/bin /sbin /usr/bin" # complete or re-order as needed on your system...

for dir in $shouldbefirst

do

   if ( echo "$UNIQUE_LIST" | grep "$dir" >/dev/null 2>/dev/null)

   then #we have this dir in UNIQUE_LIST

      NEWLIST="${NEWLIST}:${dir}"

      UNIQUE_LIST="$( echo "$UNIQUE_LIST" | grep -v "^$dir$")"  #we treated that one, take it out of the original list

   fi

done



# then put the remaining of UNIQUE_LIST in the order you want (here, alphabetically)

for dir in $UNIQUE_LIST

do 

   NEWLIST="${NEWLIST}:${dir}"

   UNIQUE_LIST="$( echo "$UNIQUE_LIST" | grep -v "^$dir$")"  #we treated that one, take it out of the original list

done



 # get rid of possible first ":" (as NEWLIST starts empty)

 NEWLIST="$(echo "$NEWLIST" | sed -e 's/^://')"



 # and then : (I test by placing "echo" in front, get rid of "echo" if it looks fine)

 echo PATH="$NEWLIST"

(once again, i can not test right now, but hope it helps)

NOTE: I'll add recommendation: get rid of "." in your PATH, as it will be "bumped" up to just after the SHOULDBEFIRST dirs ... ("." should always be avoided, and if used, always in the last place only, so that you can't easily bypass commands from /bin, /usr/bin, etc)