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I recently added this line to my .bashrc file so that I could use the java compiler javac from the command line (using MobaXTerm if that makes a difference)

export PATH=$PATH:"/cygdrive/c/Program Files/Java/jdk1.8.0_101/bin"

But I'm seeing multiple duplicates in my $PATH variable (note that the newlines were only added for readability)

/bin: /drives/c/Users/Justin/DOCUME~1/MobaXterm/slash/bin: /drives/c/WINDOWS: /drives/c/WINDOWS/system32: /cygdrive/c/ProgramFiles/Java/jdk1.8.0_101/bin: /cygdrive/c/ProgramFiles/Java/jdk1.8.0_101/bin: /cygdrive/c/ProgramFiles/Java/jdk1.8.0_101/bin

Is there something wrong with the way I'm adding to my $PATH?

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  • Take a look at: unix.stackexchange.com/questions/40749/… Commented May 28, 2017 at 21:21
  • Did you mean to say export PATH=$PATH:"/cygdrive/c/ProgramFiles/Java/jdk1.8.0_101/bin"? Commented May 28, 2017 at 21:23
  • Unless you are repeatedly sourcing your bashrc, then that path should be set once, unless it is being set somewhere else as well. Commented May 28, 2017 at 21:28

2 Answers 2

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If PATH is manipulated by different scripts that are called by .bashrc, this is usually the result.

While duplicates in PATH aren't a major problem, there are two approaches to keeping PATH free of them:

  1. Check if a dir already exists in PATH before adding
  2. Dedupe PATH as the last step in your .bashrc

Check before adding

javabin="/cygdrive/c/ProgramFiles/Java/jdk1.8.0_101/bin" if ! [[ $PATH =~ "$javabin" ]]; then PATH="$PATH:$javabin" fi

or write a function:

add_to_path() { local dir re for dir; do re="(^$dir:|:$dir:|:$dir$)" if ! [[ $PATH =~ $re ]]; then PATH="$PATH:$dir" fi done } add_to_path "/cygdrive/c/ProgramFiles/Java/jdk1.8.0_101/bin"

Dedupe (the best method I found on SO)

PATH="$(perl -e 'print join(":", grep { not $seen{$_}++ } split(/:/, $ENV{PATH}))')"

See also on Unix & Linux / SuperUser StackExchange:

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3 Comments

Will <<< not put an extra newline at the end of the last path?
Good point, @123. I replaced the awk solution with something more elegant I found here: unix.stackexchange.com/a/149054/201820
Yes, thanks for pointing that out. I have a bash alias that sources my .bashrc
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There is a function called pathmunge defined in /etc/profile:

pathmunge () { case ":${PATH}:" in *:"$1":*) ;; *) if [ "$2" = "after" ] ; then PATH=$PATH:$1 else PATH=$1:$PATH fi esac }

Unfortunately, it is also unset at the end of the file. However, just delete the unset line, and you can use it in .bashrc file.

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There is no pathmunge function in /etc/profile on my system, and I don't recommend modifying system files like that. It would be better to define pathmunge in your own .bashrc or .bash_profile.
@KeithThompson It's on Redhat, top of the file literally says It's NOT a good idea to change this file unless you know what you are doing. It's much better to create a custom.sh shell script in /etc/profile.d/ to make custom changes to your environment, as this will prevent the need for merging in future updates.
@123: Sure, but it's even better to make custom shell scripts in your home directory. Mucking around in /etc/profile.d makes sense only if you want to make things available to all users on the system. (A lot of systems these days only have one user, but it's still a useful distinction.)
@KeithThompson I wasn't arguing, I was agreeing that /etc/profile shouldn't be changed. I quoted the whole comment but the relevant part was It's NOT a good idea to change this file unless you know what you are doing.

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