Find out what scripts are being run by bash at login

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 list 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:

# prepends the given path(s) to the supplied PATH variable
# ex. add_to_path 'PATH' "$(go env GOPATH)/bin"
function add_to_path() {
    # (P)1 path is expanded from $1
    # ##: Removes leading :
    local -x pth="${(P)1##:}"
    # (s.:.) splits the given variable at :
    for p in ${(s.:.)2}; do
        # %%/ Remove trailing /
        # :P Behaves similar to realpath(3)
        local p="${${p%%/}:P}"
        if [[ ! "$pth" =~ "$p" ]]; then
            pth="$p:$pth"
        fi
    done
    export "$1"="${pth%%:}"
}

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

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

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

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

echo exit | strace bash -li |& 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.

Method 2

Reviving this question because strace is an overkill here.

Execute bash and carve it out of the output. -li is login interactively, -x prints out what bash is doing internally, and -c exit tells bash to terminate immediately. Using sed to filter out the source command or the . alias.

/bin/bash -lixc exit 2>&1 | sed -n 's/^+* (source|.) //p'

Method 3

Please consider this explanation about why ~/.profile is loaded twice.

On most Linux systems where a GUI is running the ~/.profile file is already processed at the moment you login via the GUI. When you subsequently open a terminal window, the shell should normally not be started as a login shell unless you have a very specific use-case. By default most GUIs on Linux distros have this behaviour correctly implemented.

For reference you can read the second paragraph in answer https://unix.stackexchange.com/a/119675/521859 where this is explained.

If you do start a terminal from the GUI and specify that the shell needs to use the login option, then that is very likely loading ~/.profile a second time.

You can verify if this is the case in a comparison by logging in via TTY or SSH and then check if your problem of duplicate configuration is solved. Or you can verify/disable the shell login option in your terminal program in the GUI.

Regards, Jeffrey

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0