实用的Shell(二)

本文的主线 Shell => Profile=> Env

本文环境基于Ubuntu1604 => vagrant up

Shell

echo $SHELL
# /bin/sh
echo $0
# -sh

ls -l /bin/sh
# lrwxrwxrwx 1 root root 4 Feb 18  2016 /bin/sh -> dash
cat /etc/shells
# /bin/sh
# /bin/dash
# /bin/bash
# ...

grep op /etc/passwd
# op:x:1002:1002::/home/op:
sudo usermod --shell /bin/bash op
grep op /etc/passwd
# op:x:1002:1002::/home/op:/bin/bash

• 退出后重新登录

echo $SHELL
# /bin/bash
echo $0
# -bash

bash

echo $SHELL
# /bin/bash
echo $0
# bash

Profile

cat /etc/profile
# $PS1
# /etc/profile.d/*.sh
cat ~/.profile
# $HOME/.bashrc
cat ~/.bashrc
# $PS1
# alias
# PATH
# JAVA_HOME

sudo vim /etc/profile
# TEST="/etc/profile"
vim ~/.profile
# TEST+=":~/.profile"
vim ~/.bashrc
# TEST+=":~/.bashrc"

Env

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echo $TEST
# /etc/profile:~/.bashrc:~/.profile
echo $0
# -bash

bash

echo $TEST
# :~/.bashrc
echo $0
# bash

bash --login

echo $TEST
# /etc/profile:~/.bashrc:~/.profile
echo $0
# bash

	login shell	non-login shell
定义	A login shell is a shell given to a user upon login into their user account. This is initiated by using the -l or --login option, or placing a dash as the initial character of the command name, for example invoking bash as -bash	Non-login shell, also called a sub shell is a shell started after the login process without the -l or --login option and without an extra dash before the command name
配置	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	bash reads and executes commands from /etc/bash.bashrc and ~/.bashrc, if these files exist
使用	Accessing your computer remotely using ssh Simulating an initial login shell with bash -l or sh -l "su -"切换至指定用户的login shell	其他

互动: 执行shell脚本时的TEST值?

vim test.sh

#! /bin/bash
echo $TEST

chmod +x test.sh

./test.sh

参考

• Login shells

• login shell与non-login shell的区别

• Python拾遗 - Shebang