I typed the command echo $0
in tty1, and it returned -bash
, why not bash
?
1 Answer
It indicates that bash
was started as a login shell. From man bash
, section INVOCATION
(emphasis mine):
A login shell is one whose first character of argument zero is a -, or
one started with the --login option.
...
When bash is invoked as an interactive login shell, or as a non-inter‐
active shell with the --login option, it first reads and executes com‐
mands 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.
$0
, of course, is argument zero.
In Ubuntu, typically .profile
exists and .bash_profile
and .bash_login
don't. So, a login shell reads .profile
.
See also: