If arguments remain after option processing, and neither the -c nor the -s option has been supplied, the first argument
is assumed to be the name of a file containing shell commands. If bash is invoked in this fashion, $0 is set to the name
of the file, and the positional parameters are set to the remaining arguments. Bash reads and executes commands from
this file, then exits. Bash’s exit status is the exit status of the last command executed in the script. If no commands
are executed, the exit status is 0. An attempt is first made to open the file in the current directory, and, if no file
is found, then the shell searches the directories in PATH for the script.
A login shell is one whose first character of argument zero is a -, or one started with the –login option.
An interactive shell is one started without non-option arguments and without the -c option whose standard input and error
are both connected to terminals (as determined by isatty(3)), or one started with the -i option. PS1 is set and $-
includes i if bash is interactive, allowing a shell script or a startup file to test this state.
The following paragraphs describe how bash executes its startup files. If any of the files exist but cannot be read,
bash reports an error. Tildes are expanded in file names as described below under Tilde Expansion in the EXPANSION sec‐
When bash is invoked as an interactive login shell, or as a non-interactive shell with the –login option, it first reads
and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for
~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that
exists and is readable. The –noprofile option may be used when the shell is started to inhibit this behavior.
When a login shell exits, bash reads and executes commands from the file ~/.bash_logout, if it exists.
When an interactive shell that is not a login shell is started, bash reads and executes commands from /etc/bash.bashrc
and ~/.bashrc, if these files exist. This may be inhibited by using the –norc option. The –rcfile file option will
force bash to read and execute commands from file instead of /etc/bash.bashrc and ~/.bashrc.