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Do you read manpage?
man bash
...
INVOCATION
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 output are both connected to terminals (as determined
by isatty(3)), or one started with the -i option. PS1 is
set and $- includes i if bash is interactive, allowing a
shell script or a startup file to test this state.
The following paragraphs describe how bash executes its
startup files. If any of the files exist but cannot be
read, bash reports an error. Tildes are expanded in file
names as described below under Tilde Expansion in the
EXPANSION section.
When bash is invoked as an interactive login shell, or as
a non-interactive shell with the --login option, it first
reads and executes commands from the file /etc/profile, if
that file exists. After reading that file, it looks for
~/.bash_profile, ~/.bash_login, and ~/.profile, in that
order, and reads and executes commands from the first one
that exists and is readable. The --noprofile option may
be used when the shell is started to inhibit this behav-
ior.
When a login shell exits, bash reads and executes commands
from the file ~/.bash_logout, if it exists.
When an interactive shell that is not a login shell is
started, bash reads and executes commands from ~/.bashrc,
if that file exists. This may be inhibited by using the
--norc option. The --rcfile file option will force bash
to read and execute commands from file instead of
~/.bashrc.
When bash is started non-interactively, to run a shell
script, for example, it looks for the variable BASH_ENV in
the environment, expands its value if it appears there,
and uses the expanded value as the name of a file to read
and execute. Bash behaves as if the following command
were executed:
if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
but the value of the PATH variable is not used to search
for the file name.
If bash is invoked with the name sh, it tries to mimic the
startup behavior of historical versions of sh as closely
as possible, while conforming to the POSIX standard as
well. When invoked as an interactive login shell, or a
non-interactive shell with the --login option, it first
attempts to read and execute commands from /etc/profile
and ~/.profile, in that order. The --noprofile option may
be used to inhibit this behavior. When invoked as an
interactive shell with the name sh, bash looks for the
variable ENV, expands its value if it is defined, and uses
the expanded value as the name of a file to read and exe-
cute. Since a shell invoked as sh does not attempt to
read and execute commands from any other startup files,
the --rcfile option has no effect. A non-interactive
shell invoked with the name sh does not attempt to read
any other startup files. When invoked as sh, bash enters
posix mode after the startup files are read.
When bash is started in posix mode, as with the --posix
command line option, it follows the POSIX standard for
startup files. In this mode, interactive shells expand
the ENV variable and commands are read and executed from
the file whose name is the expanded value. No other
startup files are read.
Bash attempts to determine when it is being run by the
remote shell daemon, usually rshd. If bash determines it
is being run by rshd, it reads and executes commands from
~/.bashrc, if that file exists and is readable. It will
not do this if invoked as sh. The --norc option may be
used to inhibit this behavior, and the --rcfile option may
be used to force another file to be read, but rshd does
not generally invoke the shell with those options or allow
them to be specified.
If the shell is started with the effective user (group) id
not equal to the real user (group) id, and the -p option
is not supplied, no startup files are read, shell func-
tions are not inherited from the environment, the SHEL-
LOPTS variable, if it appears in the environment, is
ignored, and the effective user id is set to the real user
id. If the -p option is supplied at invocation, the
startup behavior is the same, but the effective user id is
not reset. |
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楼主: Ericzhao82
发表于 2006-02-21 13:47
发表于 2006-02-21 13:49
