12

After starting a bash terminal, I noticed that the PATH variable contains duplicate entries. My terminal starts a login shell, so ~/.bash_profile is sourced, followed by ~/.profile and ~/.bashrc. Only in ~/.profile do I create the paths entries which are duplicated.

To be pedantic, this is the order in which the files that SHOULD be sourced are being sourced:

Sourced /etc/profile
Sourced /etc/bash.bashrc
Sourced .bash_profile
Sourced .profile
Sourced .bashrc

Before anyone marks this as a duplicate of "PATH variable contains duplicates", keep reading.

At first I thought this had to do with ~/.profile being sourced twice, so I had the file write to a log file whenever it was sourced, and surprisingly it only logged one entry, which tells me that it was only sourced once. Even more surprising is the fact that when I comment out the entries which were in ~/.profile, the entries still appear in the PATH variable. This has led me to three conclusions, one of which was quickly ruled out:

  1. Bash ignores valid bash comments and still executes the commented code
  2. There is a script which reads the ~/.profile and ignores any code that prints an output (the log file for example)
  3. There is another copy of my ~/.profile which is being sourced elsewhere

The first one, I quickly concluded not to be the case due to some quick testing. The second and third options are where I need help with.

How do I gather a log of scripts which are executed when my terminal starts up? I used echo in the files that I checked to know if they are sourced by bash, but I need to find a conclusive method which traces the execution up the point when the terminal is ready for me to start typing into it.

If the above is not possible, then can anyone suggest where else I can look to see which scripts are being run.


Future reference

This is the script I now use for adding to my path:

function add_to_path() {
    for path in ${2//:/ }; do
        if ! [[ "${!1}" =~ "${path%/}" ]]; then # ignore last /
            new_path="$path:${!1#:}"
            export "$1"="${new_path%:}" # remove trailing :
        fi
    done
}

I use it like this:

add_to_path 'PATH' "/some/path/bin"

The script checks if the path already exists in the variable before prepending it.

For zsh users, you can use this equivalent:

function add_to_path() {
    for p in ${(s.:.)2}; do
        if [[ ! "${(P)1}" =~ "${p%/}" ]]; then
            new_path="$p:${(P)1#:}"
            export "$1"="${new_path%:}"
        fi
    done
}

Edit 28/8/2018

One more thing I found I could do with this script is to also fix the path. So at the start of my .bashrc file, I do something like this:

_temp_path="$PATH"
PATH='/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin'
add_to_path 'PATH' "$_temp_path"
unset _temp_path

It is up to you what the PATH should start with. Examine PATH first to decide.

24

If your system has strace then you can list the files opened by the shell, for example using

echo exit | strace bash -li |& less | grep '^open'

(-li means login shell interactive; use only -i for an interactive non-login shell.)

This will show a list of files which the shell opened or tried to open. On my system, they are as follows:

  1. /etc/profile
  2. /etc/profile.d/* (various scripts in /etc/profile.d/)
  3. /home/<username>/.bash_profile (this fails, I have no such file)
  4. /home/<username>/.bash_login (this fails, I have no such file)
  5. /home/<username>/.profile
  6. /home/<username>/.bashrc
  7. /home/<username>/.bash_history (history of command lines; this is not a script)
  8. /usr/share/bash-completion/bash_completion
  9. /etc/bash_completion.d/* (various scripts providing autocompletion functionality)
  10. /etc/inputrc (defines key bindings; this is not a script)

Use man strace for more information.

  • Thanks for your input, but I think there is something seriously wrong with my bash. Running echo $0 in the terminal gives -bash rather than the expected bash. Do you have any other suggestions for this? – smac89 Jan 2 '17 at 22:15
  • 2
    @smac89: That's normal for a login shell. Bash behaves as a login shell when the 1st character of $0 is a dash -, or when invoked with the option -l. – AlexP Jan 2 '17 at 22:16
  • OK that's a bit of a relief. I have ran the command you gave and the output looks really complicated, but nonetheless all the files shown do not contain the duplicated entries. This is leading me to think that the duplicated entries happen when I first log into my account, i.e. something is initially sourcing the entries in that file and it is done again when I open the terminal? Actually I think that might be it. When I log in to my account, the entries are sourced, and again when I open the terminal the process is repeated. Does that sound possible? – smac89 Jan 2 '17 at 22:24
  • Why don't you debug the old fashioned way, by putting echo PATH=\""$PATH"\" at the beginning and end of .profile and .bashrc? And why don't you do what everybody does and set the PATH either fully, or, if adding a directory, guarded: echo ":$PATH:" | grep -q ":/path/to/dir:" || export PATH="$PATH:/path/to/dir"? – AlexP Jan 2 '17 at 22:26
  • 2
    Use sudo bash -c "echo exit|dtruss bash -li|& less|grep '^open'" on macOS. (just replace strace with dtruss) – Max Coplan Nov 19 '18 at 23:37

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