Hi,
I was trying to set python path,
and I think I accidentally misplaced an export command
currently my terminal begins like this

Last login: Mon Oct 2 16:28:18 on ttys000
-bash: export: `/abin': not a valid identifier
-bash: PYTHONPATH: command not found
export: Command not found.
export: Command not found.

can I get some help?
Can I reset the bash profile /profile/ bashrc to go back to the beginning?

Unless you have made a backup copy of your bashrc file, the only other way I can think of to restore it would be;

Load/Install a copy of the *same* Linux distro into a virtual machine and copy the bashrc file from that, to your 'real' system.

Best of luck with it.

Welcome to LQ!!! Try the -vx shell switches, to debug what exactly is happening.

Can you post the relevant exerpt from whatever file you changed? (http://termbin.com may help post info)

Hi, welcome to LQ,

Please just post a copy of your bash profile here using the CODE construct and we will certainly be able to help you better. Make sure you give precisions about the file. Is it the system-wide profile in /etc or is it your home profile?

-bash: indicates it is the login shell and that primarily reads .bash_profile if present, otherwise .profile.
Some Linux vendors put something in the system-wide /etc/profile that includes .bashrc, so this might be used secondary.

I cannot open my bash_profile using nano command, and when I try to open on finder, it just shows few lines, which I don't think is the whole part

it only shows

if [-f ~/.bashrc]; then
source ~/.bashrc
fi

when I do echo $PATH it shows double path, like this

[Cogs-iMac:~] coglab% echo $PATH
$ath:/Users/coglab/abin:/Users/coglab/abin

if you want to restore the "official" default - you may try to create another user and use that .bashrc.
But it looks like your PATH variable is not set properly, you need to fix only that.

Which file did you originally modify .bash_profile or .bashrc?

Obviously it depends on the distribution but your looks normal. Below is the default .bash_profile from CentOS. As posted the system wide defaults are located in /etc and user specific environment is defined in your ~/.bash_profile.
Without knowing exactly what you did to mess things up try logging out and back in.

that is the crucial question.
there's also a few more files that might be responsible, e.g. ~/.profile
and all 3 files mentioned have systemwide counterparts in /etc.

The original versions of files that get installed when your account is created are typically found in /etc/skel.

Hi again....have faith: the LQ'ers will 'get you there'; we just need to find out what got changed, out of the several files involved in logging-in. (Feel free to web-research for the sequence.) Which distro? MacOS?

IF your shell 'lost' its path, you can explicitly run cmds with their full path, like:
/usr/bin/nano (or /bin/cat; there's also sbin) (or maybe MacOS doesn't have nano)

If your internet is working, you can use that 'pipe to nc port 9999'
(cmd1;cmd2;...)|netcat termbin.com 9999, to just post 4char (link)

Those 'code' tags keep $:path :P smileys away. Unix is case-sensitive.

Look for relevant file that has: abin plus another 'typo' in it, around where ?you? (or py?) put abin (maybe; is abin a typo?)

Just want to point out that OP appears to be using a Mac/OS X. Granted, bash and these config files should work roughly the same way (I know they have for me), but for more specific support you might want to reach out to a Mac forum, or at the very least a BSD forum... just in case your problem has something to do with OS X and not bash specifically.

If this is your .bash_profile, then the code does include your .bashrc
I.e.you must look at your .bashrc to find more(most) code.

Normally your home bash_profile will be at ~/.bash_profile. As you see, from your investigation, it sources ~/.bashrc. So look in that direction. If .bashrc sources another script, follow the lead until you find out what line from which file specifically is breaking your PATH variable.