你可能不知道的shell、bash二三事（Centos 7）

个人.bashrc：

~/.bashrc：

# .bashrc

# User specific aliases and functions

alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'

# Source global definitions
if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi

全局bashrc：

/etc/bashrc:

# /etc/bashrc

# System wide functions and aliases
# Environment stuff goes in /etc/profile

# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.

# are we an interactive shell?
if [ "$PS1" ]; then
  if [ -z "$PROMPT_COMMAND" ]; then
    case $TERM in
    xterm*|vte*)
      if [ -e /etc/sysconfig/bash-prompt-xterm ]; then
          PROMPT_COMMAND=/etc/sysconfig/bash-prompt-xterm
      elif [ "${VTE_VERSION:-0}" -ge  ]; then
          PROMPT_COMMAND="__vte_prompt_command"
      else
          PROMPT_COMMAND='printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'
      fi
      ;;
    screen*)
      if [ -e /etc/sysconfig/bash-prompt-screen ]; then
          PROMPT_COMMAND=/etc/sysconfig/bash-prompt-screen
      else
          PROMPT_COMMAND='printf "\033k%s@%s:%s\033\\" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'
      fi
      ;;
    *)
      [ -e /etc/sysconfig/bash-prompt-default ] && PROMPT_COMMAND=/etc/sysconfig/bash-prompt-default
      ;;
    esac
  fi
  # Turn on parallel history
  shopt -s histappend
  history -a
  # Turn on checkwinsize
  shopt -s checkwinsize
  [ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@\h \W]\\$ "
  # You might want to have e.g. tty in prompt (e.g. more virtual machines)
  # and console windows
  # If you want to do so, just add e.g.
  # if [ "$PS1" ]; then
  #   PS1="[\u@\h:\l \W]\\$ "
  # fi
  # to your custom modification shell script in /etc/profile.d/ directory
fi

if ! shopt -q login_shell ; then # We're not a login shell
    # Need to redefine pathmunge, it get's undefined at the end of /etc/profile
    pathmunge () {
        case ":${PATH}:" in
            *:"$1":*)
                ;;
            *)
                if [ "$2" = "after" ] ; then
                    PATH=$PATH:$
                else
                    PATH=$:$PATH
                fi
        esac
    }
    # By default, we want umask to get set. This sets it for non-login shell.
    # Current threshold for system reserved uid/gids is
    # You could check uidgid reservation validity in
    # /usr/share/doc/setup-*/uidgid file
    if [ $UID -gt  ] && [ "`/usr/bin/id -gn`" = "`/usr/bin/id -un`" ]; then
       umask
    else
       umask
    fi

    SHELL=/bin/bash
    # Only display echos from profile.d scripts if we are no login shell
    # and interactive - otherwise just process them to set envvars
    for i in /etc/profile.d/*.sh; do
        if [ -r "$i" ]; then
            if [ "$PS1" ]; then
                . "$i"
            else
                . "$i" >/dev/null
            fi
        fi
    done

    unset i
    unset -f pathmunge
fi
# vim:ts=4:sw=4

用户的bashprofile：

~/.bash_profile

# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

# User specific environment and startup programs

PATH=$PATH:$HOME/bin

export PATH

[root@ckl1 bashtest]# echo $HOME
/root

全局profile：

"/etc/profile"

# /etc/profile

# System wide environment and startup programs, for login setup
# Functions and aliases go in /etc/bashrc

# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.

pathmunge () {
    case ":${PATH}:" in
        *:"$1":*)
            ;;
        *)
            if [ "$2" = "after" ] ; then
                PATH=$PATH:$
            else
                PATH=$:$PATH
            fi
    esac
}

if [ -x /usr/bin/id ]; then
    if [ -z "$EUID" ]; then
        # ksh workaround
        EUID=`/usr/bin/id -u`
        UID=`/usr/bin/id -ru`
    fi
    USER="`/usr/bin/id -un`"
    LOGNAME=$USER
    MAIL="/var/spool/mail/$USER"
fi

# Path manipulation
if [ "$EUID" = "" ]; then
    pathmunge /usr/sbin
    pathmunge /usr/local/sbin
else
    pathmunge /usr/local/sbin after
    pathmunge /usr/sbin after
fi

HOSTNAME=`/usr/bin/hostname >/dev/null`
HISTSIZE=
if [ "$HISTCONTROL" = "ignorespace" ] ; then
    export HISTCONTROL=ignoreboth
else
    export HISTCONTROL=ignoredups
fi

export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL

# By default, we want umask to get set. This sets it for login shell
# Current threshold for system reserved uid/gids is
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt  ] && [ "`/usr/bin/id -gn`" = "`/usr/bin/id -un`" ]; then
    umask
else
    umask
fi

for i in /etc/profile.d/*.sh ; do
    if [ -r "$i" ]; then
        if [ "${-#*i}" != "$-" ]; then
            . "$i"
        else
            . "$i" >/dev/null
        fi
    fi
done

unset i
unset -f pathmunge

#java environment
export JAVA_HOME=/usr/local/jdk1.8.0_161
export CLASSPATH=.:${JAVA_HOME}/jre/lib/rt.jar:${JAVA_HOME}/lib/dt.jar:${JAVA_HOME}/lib/tools.jar
export PATH=$PATH:${JAVA_HOME}/bin

关于别名：

别名，典型的如ll，是ls -l 的别名，那么这个别名定义在哪呢，其实是在/etc/profile.d/colorls.sh 中，也就是我在上面几个文件中，标红的部分。

colorls.sh：

# color-ls initialization

# Skip all for noninteractive shells.
[ ! -t  ] && return

#when USER_LS_COLORS defined do not override user LS_COLORS, but use them.
if [ -z "$USER_LS_COLORS" ]; then

  alias ll='ls -l' >/dev/null
  alias l.='ls -d .*' >/dev/null

  INCLUDE=
  COLORS=

  for colors in "$HOME/.dir_colors.$TERM" "$HOME/.dircolors.$TERM" \
      "$HOME/.dir_colors" "$HOME/.dircolors"; do
    [ -e "$colors" ] && COLORS="$colors" && \
    INCLUDE="`/usr/bin/cat "$COLORS" | /usr/bin/grep '^INCLUDE' | /usr/bin/cut -d ' ' -f2-`" && \
    break
  done

  [ -z "$COLORS" ] && [ -e "/etc/DIR_COLORS.$TERM" ] && \
  COLORS="/etc/DIR_COLORS.$TERM"

  [ -z "$COLORS" ] && [ -e "/etc/DIR_COLORS.256color" ] && \
  [ "x`/usr/bin/tty -s && /usr/bin/tput colors 2>/dev/null`" = "x256" ] && \
  COLORS="/etc/DIR_COLORS.256color"

  [ -z "$COLORS" ] && [ -e "/etc/DIR_COLORS" ] && \
  COLORS="/etc/DIR_COLORS"

  # Existence of $COLORS already checked above.
  [ -n "$COLORS" ] || return

  if [ -e "$INCLUDE" ];
  then
    TMP="`/usr/bin/mktemp .colorlsXXX -q --tmpdir=/tmp`"
    [ -z "$TMP" ] && return

    /usr/bin/cat "$INCLUDE" >> $TMP
    /usr/bin/grep -v '^INCLUDE' "$COLORS" >> $TMP

    eval "`/usr/bin/dircolors --sh $TMP 2>/dev/null`"
    /usr/bin/rm -f $TMP
  else
    eval "`/usr/bin/dircolors --sh $COLORS 2>/dev/null`"
  fi

  [ -z "$LS_COLORS" ] && return
  /usr/bin/grep -qi "^COLOR.*none" $COLORS >/dev/null >/dev/null && return
fi

unset TMP COLORS INCLUDE

alias ll='ls -l --color=auto' >/dev/null
alias l.='ls -d .* --color=auto' >/dev/null
alias ls='ls --color=auto' >/dev/null
(END)

所以，什么情况下可以执行别名呢：

1：执行了/etc/profile

2：执行了~/.bashrc，~/.bashrc中引用了 /etc/bashrc（在该文件中，执行了ll别名所在的colorls.sh文件）

3：执行了~/.bash_profile，因为该文件中判断是否存在~/.bashrc，存在的话，会去执行~/.bashrc；根据上一步的结论，自然也就可以执行别名。

ok。那么，进一步，什么情况会执行上述的两种情况：

第一种情况（/etc/profile）：

查阅了man bash后，发现：

1.交互的登录shell，或者--login选项的非交互shell。

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.

不过在我的centos7中，~/.profile不存在。

第二种情况（~/.bashrc）：

1.交互的，但不是登录的shell。

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.

第三种情况（~/.bash_profile）:

同情况1。

Shell的几种类型：

ok。那么看了上面两种还是很蒙，那么我们再科普下什么是交互shell、非交互shell、登录shell和非登录shell。

我是参考了这里：https://blog.csdn.net/wisgood/article/details/52043522

我的理解：

登录shell：

ssh登录的，就是登录shell，登录shell要退出的话，是执行logout。比如我们用的putty、securtCRT。

非登录shell：

登录成功了之后，或者并没有进行远程登录，直接就在本机的（VMVARE的虚拟机中的shell都不能算，可采用下面的方法测试）ubuntu打开终端，这种，我理解的就是非登录shell。

我做了个小实验，我是secureCRT远程到该服务器的，在/home/upload/bashtest/a.sh中，我写了句logout：

[root@ckl1 bashtest]# less a.sh
#/bin/bash

logout

执行该脚本：

[root@ckl1 bashtest]# ./a.sh 

结果：

./a.sh: line 3: logout: not login shell: use `exit'

区分登录与非登录shell的好办法：

（https://unix.stackexchange.com/questions/38175/difference-between-login-shell-and-non-login-shell）

1.通过echo $0，如果结果是-bash，那就是login shell。否则不是。

2.如果可以执行logout命令，那么就是login shell；否则不是。

交互shell：

就是我们不管是用SecurtCRT这样的工具进入远程服务器也好，或者本机打开终端也好，都可以执行各种命令

在执行这些命令时，shell是可以和我们互动的，比如要求我们输入东西，比如按Tab可以提示，等等。

非交互Shell：

shell脚本执行，一般来说就是非交互的，我们写好了脚本，只要交给shell执行就好，期间不需要和我们交互。命令输入错了，会直接提示并退出。

以上两种，其实是不同维度，可以两两组合

	交互	非交互
登录	远程登录ssh,调用的文件包括：/etc/profile，~/.bash_profile，~/.bash_login,~/.profile	较少见，可能读/etc/profile ， ~/.profile。也可能不读。依然请参考第一个答案：https://unix.stackexchange.com/questions/38175/difference-between-login-shell-and-non-login-shell
非登录	本机打开终端，调用文件包括：~/.bashrc	执行shell脚本，调用文件包括：BASH_ENV 指定的文件

非交互shell中，怎么才能使用别名：

参考：

https://stackoverflow.com/questions/1615877/why-aliases-in-a-non-interactive-bash-shell-do-not-work

方式1:

shopt -s expand_aliases

不过我的centos 7，未生效。

方式2：

source their .bashrc at the end of their profile。

也就是在~/.bash_profile中新增一行：source ~/.bashrc

但是我这边依然没生效。

方式3：

直接脚本中增加：source ~/.bashrc

#/bin/bash
ls -l

echo "ll "
source ~/.bashrc

ll

ok。可以正常工作。

ssh执行远程命令时，怎么才能使用别名：

1.

首先修改远程主机的~/.bashrc,新增一行：

shopt -s expand_aliases

 再使用：

ssh -t @host ll

2.

ssh @host 'bash -ci ll'

参考：

https://stackoverflow.com/questions/1198378/ssh-command-execution-doesnt-consider-bashrc-bash-login-ssh-rc

https://stackoverflow.com/questions/1615877/why-aliases-in-a-non-interactive-bash-shell-do-not-work