phx13ye
2015-08-29 01:41:17 +08:00
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 error are both connected
to terminals (as determined by isatty (3 )), or one started with the -i option. PS1 is set and $- includes i if bash is interactive, allowing a
shell script or a startup file to test this state.
The following paragraphs describe how bash executes its startup files. If any of the files exist but cannot be read, bash reports an error.
Tildes are expanded in filenames as described below under Tilde Expansion in the EXPANSION section.
When bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes com ‐
mands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile,
in that order, and reads and executes commands from the first one that exists and is readable. The --noprofile option may be used when the
shell is started to inhibit this behavior.
When a login shell exits, bash reads and executes commands from the file ~/.bash_logout, if it exists.
When an interactive shell that is not a login shell is started, bash reads and executes commands from ~/.bashrc, if that file exists. This
may be inhibited by using the --norc option. The --rcfile file option will force bash to read and execute commands from file instead of
~/.bashrc.
When bash is started non-interactively, to run a shell script, for example, it looks for the variable BASH_ENV in the environment, expands its
value if it appears there, and uses the expanded value as the name of a file to read and execute. Bash behaves as if the following command
were executed:
if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
but the value of the PATH variable is not used to search for the filename.
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 con ‐
forming 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 execute. Since a shell invoked as sh does not attempt to read and execute com ‐
mands 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.