自定义和使用 shell 环境

[ian@atticf22 ~]$ echo $UID
1000
[ian@atticf22 ~]$ echo $HOME
/home/ian

[ian@atticf22 ~]$ # Use the ps command to list current PID, parent PID and running command name
[ian@atticf22 ~]$ ps -p $$ -o "pid ppid cmd"
 PID  PPID CMD
12761  9169 bash
[ian@atticf22 ~]$ # Start a child bash process
[ian@atticf22 ~]$ bash
[ian@atticf22 ~]$ # Assign two variables
[ian@atticf22 ~]$ VAR1=v1
[ian@atticf22 ~]$ VAR2="Variable 2"
[ian@atticf22 ~]$ # Export examples
[ian@atticf22 ~]$ export VAR2
[ian@atticf22 ~]$ export VAR3="Assigned and exported in one step"
[ian@atticf22 ~]$ # Use the $ character to reference the variables
[ian@atticf22 ~]$ echo $VAR1 '/' $VAR2 '/' $VAR3
v1 / Variable 2 / Assigned and exported in one step
[ian@atticf22 ~]$ # What is the value of the SHELL variable?
[ian@atticf22 ~]$ echo $SHELL
/bin/bash
[ian@atticf22 ~]$ # Now start ksh child and export VAR4
[ian@atticf22 ~]$ ksh
$ ps -p $$ -o "pid ppid cmd"
 PID  PPID CMD
26212 22923 ksh
$ export VAR4=var4
$ # See what is visible
$ echo $VAR1 '/' $VAR2 '/' $VAR3 '/' $VAR4 '/' $SHELL
/ Variable 2 / Assigned and exported in one step / var4 / /bin/bash
$# No VAR1 and shell is /bin/bash - is that right?
$ exit
[ian@atticf22 ~]$ ps -p $$ -o "pid ppid cmd"
 PID  PPID CMD
22923 12761 bash
[ian@atticf22 ~]$ # See what is visible
[ian@atticf22 ~]$ echo $VAR1 '/' $VAR2 '/' $VAR3 '/' $VAR4 '/' $SHELL
v1 / Variable 2 / Assigned and exported in one step / / /bin/bash
[ian@atticf22 ~]$ # No VAR4 - our child cannot export back to us
[ian@atticf22 ~]$ exit
exit
[ian@atticf22 ~]$ ps -p $$ -o "pid ppid cmd"
 PID  PPID CMD
12761  9169 bash
[ian@atticf22 ~]$ # See what is visible
[ian@atticf22 ~]$ echo $VAR1 '/' $VAR2 '/' $VAR3 '/' $VAR4 '/' $SHELL
/ / / / /bin/bash
[ian@atticf22 ~]$ # None of VAR1 through VAR4 is exported back to parent

 [ian@atticf22 ~]$ echo $USER $UID
 ian 1000
 [ian@atticf22 ~]$ echo $SHELL $HOME $PWD
 /bin/bash /home/ian /home/ian
 [ian@atticf22 ~]$ (exit 0);echo $?;(exit 4);echo $?
 0
 4

 [ian@atticf22 ~]$ echo $0
 bash
 [ian@atticf22 ~]$ echo $$ $PPID
 12761 9169
 [ian@atticf22 ~]$ # see what my process and its parent are running
 [ian@atticf22 ~]$ ps -p $$,$PPID -o "pid ppid cmd"
  PID  PPID CMD
 9169 1 /usr/libexec/gnome-terminal-server
 12761  9169 bash

[ian@atticf22 ~]$ echo "$VAR5 / $VAR6"
/
[ian@atticf22 ~]$ VAR5=5 VAR6="some value" bash
[ian@atticf22 ~]$ echo "$VAR5 / $VAR6"
5 / some value
[ian@atticf22 ~]$ exit
[ian@atticf22 ~]$ echo "$VAR5 / $VAR6"
/

info bash "Shell Builtin Commands" "Bash Builtins"  --index-search declare

help declare

 [ian@atticf22 ~]$ declare -r rov1="this is readonly"
 [ian@atticf22 ~]$ rov="Who says it's read only?"
 [ian@atticf22 ~]$ readonly rov2="another constant value"
 [ian@atticf22 ~]$ rov2=3
 bash: rov2: readonly variable
 [ian@atticf22 ~]$ UID=99
 bash: UID: readonly variable
 [ian@atticf22 ~]$ declare -pr
 declare -r BASHOPTS="checkwinsize:cmdhist:complete_fullquote:expand_aliases:extglob:extquote:
 force_fignore:histappend:interactive_comments:progcomp:promptvars:sourcepath"
 declare -ir BASHPID
 declare -r BASH_COMPLETION_COMPAT_DIR="/etc/bash_completion.d"
 declare -ar BASH_VERSINFO='([0]="4" [1]="3" [2]="42" [3]="1" [4]="release" [5]=
"x86_64-redhat-linux-gnu")'
 declare -ir EUID="1000"
 declare -ir PPID="12761"
 declare -r SHELLOPTS="braceexpand:emacs:hashall:histexpand:history:interactive-comments:monitor"
 declare -ir UID="1000"
 declare -r rov1="this is readonly"
 declare -r rov2="another constant value"
 [ian@atticf22 ~]$ help declare
 declare: declare [-aAfFgilnrtux] [-p] [name[=value] ...]
    Set variable values and attributes.

    Declare variables and give them attributes.  If no NAMEs are given,
    display the attributes and values of all variables.

    Options:
      -f   restrict action or display to function names and definitions
      -F   restrict display to function names only (plus line number and
       source file when debugging)
      -g   create global variables when used in a shell function; otherwise
       ignored
      -p   display the attributes and value of each NAME

    Options which set attributes:
      -a   to make NAMEs indexed arrays (if supported)
      -A   to make NAMEs associative arrays (if supported)
      -i   to make NAMEs have the `integer' attribute
      -l   to convert NAMEs to lower case on assignment
      -n   make NAME a reference to the variable named by its value
      -r   to make NAMEs readonly
      -t   to make NAMEs have the `trace' attribute
      -u   to convert NAMEs to upper case on assignment
      -x   to make NAMEs export

    Using `+' instead of `-' turns off the given attribute.

    Variables with the integer attribute have arithmetic evaluation (see
    the `let' command) performed when the variable is assigned a value.

    When used in a function, `declare' makes NAMEs local, as with the `local'
    command.  The `-g' option suppresses this behavior.

    Exit Status:
    Returns success unless an invalid option is supplied or a variable
    assignment error occurs.

 [ian@atticf22 ~]$ bash
 [ian@atticf22 ~]$ VAR1=v1
 [ian@atticf22 ~]$ declare -i VAR2
 [ian@atticf22 ~]$ VAR2=3+4
 [ian@atticf22 ~]$ echo $VAR1 $VAR2
 v1 7
 [ian@atticf22 ~]$ unset VAR1
 [ian@atticf22 ~]$ echo $VAR1 $VAR2
 7
 [ian@atticf22 ~]$ unset -v VAR2
 [ian@atticf22 ~]$ echo $VAR1 $VAR2

 [ian@atticf22 ~]$ exit
 exit

 [ian@atticf22 ~]$ bash
 [ian@atticf22 ~]$ set -u
 [ian@atticf22 ~]$ VAR1=var1
 [ian@atticf22 ~]$ echo $VAR1
 var1
 [ian@atticf22 ~]$ unset VAR1
 [ian@atticf22 ~]$ echo $VAR1
 bash: VAR1: unbound variable
 [ian@atticf22 ~]$ VAR1=
 [ian@atticf22 ~]$ echo $VAR1

 [ian@atticf22 ~]$ unset VAR1
 [ian@atticf22 ~]$ echo $VAR1
 bash: VAR1: unbound variable
 [ian@atticf22 ~]$ unset -v VAR1
 [ian@atticf22 ~]$ set +u
 [ian@atticf22 ~]$ echo $VAR1

 [ian@atticf22 ~]$ exit
 exit

[ian@atticf22 ~]$ tcsh
[ian@atticf22 ~]$ setenv E1 "Env variable 1"
[ian@atticf22 ~]$ set V2="variable 2"
[ian@atticf22 ~]$ echo "$E1 / $V2"
Env variable 1 / variable 2
[ian@atticf22 ~]$ tcsh
[ian@atticf22 ~]$ echo $E1
Env variable 1
[ian@atticf22 ~]$ echo $V2
V2: Undefined variable.
[ian@atticf22 ~]$ echo "$?E1 / $?V2"
1 / 0
[ian@atticf22 ~]$ exit

[ian@atticf22 ~]$ echo "$E1 / $V2"
Env variable 1 / variable 2
[ian@atticf22 ~]$ set E1="I'm now a regular variable"
[ian@atticf22 ~]$ echo $E1
I'm now a regular variable
[ian@atticf22 ~]$ unset E1
[ian@atticf22 ~]$ echo $E1
Env variable 1
[ian@atticf22 ~]$ unsetenv E1
[ian@atticf22 ~]$ echo $E1
E1: Undefined variable.

 [ian@atticf22 ~]$ cat ~/.bash_profile
 # .bash_profile

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

 # User specific environment and startup programs

 PATH=$PATH:$HOME/.local/bin:$HOME/bin

 export PATH

 [ian@atticf22 ~]$ echo VAR1=var1>testrc
 [ian@atticf22 ~]$ echo $VAR1

 [ian@atticf22 ~]$ bash --rcfile testrc
 bash-4.3$ echo $VAR1
 var1
 bash-4.3$ exit
 exit

$include /etc/inputrc

[ian@atticf22 ~]$ cat testenv.sh
#!/bin/bash
echo "Test of BASH_ENV"
export VAR_ENV="my value"
[ian@atticf22 ~]$ cat testscript.sh
#!/bin/bash
echo "Running $0"
echo "VAR_ENV is set to $VAR_ENV"
[ian@atticf22 ~]$ ./testscript.sh
Running ./testscript.sh
VAR_ENV is set to
[ian@atticf22 ~]$ export BASH_ENV="~/testenv.sh"
[ian@atticf22 ~]$ ./testscript.sh
Test of BASH_ENV
Running ./testscript.sh
VAR_ENV is set to my value

[ian@atticf22 ~]$ (ls -lrS /usr/bin; du /usr/bin) | tail -n 3
-rwxr-xr-x.   1 root root    10669512 Sep 18 10:41 mysql
-rwxr-xr-t.   1 root root    15148768 Sep 14 05:11 emacs-24.5
386296   /usr/bin
[ian@atticf22 ~]$ { ls -lrS /usr/bin; du /usr/bin; } | tail -n 3
-rwxr-xr-x.   1 root root    10669512 Sep 18 10:41 mysql
-rwxr-xr-t.   1 root root    15148768 Sep 14 05:11 emacs-24.5
386296   /usr/bin

[ian@atticf22 ~]$ # Two commonly set aliases
[ian@atticf22 ~]$ alias ls ll
alias ls='ls --color=auto'
alias ll='ls -l --color=auto'
[ian@atticf22 ~]$ # Add one for a long listing in reverse chronological order
[ian@atticf22 ~]$ alias llrt='ls -lrt --color=auto'
[ian@atticf22 ~]$ llrt /bin
lrwxrwxrwx. 1 root root 7 Aug 16  2014 /bin -> usr/bin
[ian@atticf22 ~]$ # Remove our new alias
[ian@atticf22 ~]$ unalias llrt
[ian@atticf22 ~]$

[ian@atticf22 ~]$ alias which
alias which='(alias; declare -f) | /usr/bin/which --tty-only --read-alias \
--read-functions --show-tilde --show-dot'
[ian@atticf22 ~]$ which which
alias which='(alias; declare -f) | /usr/bin/which --tty-only --read-alias \
--read-functions --show-tilde --show-dot'
  /usr/bin/which

[ian@atticf22 developerworks]$ # Wrong way
[ian@atticf22 developerworks]$ alias lsdu=ls;du -sh
8.2M    .
[ian@atticf22 developerworks]$ lsdu
new-article.py        new-article.vbs  schema     tools        web
new-article-rich.vbs  readme           templates  validate.py  xsl
[ian@atticf22 developerworks]$ # Right way
[ian@atticf22 developerworks]$ alias lsdu='ls;du -sh'
[ian@atticf22 developerworks]$ lsdu
new-article.py        new-article.vbs  schema     tools        web
new-article-rich.vbs  readme           templates  validate.py  xsl
8.2M    .

[ian@atticf22 ~]$ alias mypwd1='echo Current directory is $PWD'
[ian@atticf22 ~]$ alias mypwd2="echo Current directory is $PWD"
[ian@atticf22 ~]$ # cd to a different directory
[ian@atticf22 ~]$ cd developerworks
[ian@atticf22 developerworks]$ mypwd1
Current directory is /home/ian/developerworks
[ian@atticf22 developerworks]$ mypwd2
Current directory is /home/ian
[ian@atticf22 developerworks]$ alias mypwd1 mypwd2
alias mypwd1='echo Current directory is $PWD'
alias mypwd2='echo Current directory is /home/ian'

[ian@atticf22 ~]$ ls -l developerworks/ | grep "^d"
drwxrwxr-x. 2 ian ian  4096 Nov 13 13:06 my first article
drwxrwxr-x. 2 ian ian  4096 Sep 12  2014 readme
drwxrwxr-x. 4 ian ian  4096 Sep 12  2014 schema
drwxrwxr-x. 3 ian ian  4096 Sep 12  2014 templates
drwxrwxr-x. 3 ian ian  4096 Sep 12  2014 tools
drwxrwxr-x. 3 ian ian  4096 Mar  5  2013 web
drwxrwxr-x. 4 ian ian  4096 Sep 12  2014 xsl

[ian@atticf22 ~]$ ls -F developerworks/ | grep "/$"
my first article/
readme/
schema/
templates/
tools/
web/
xsl/

[ian@atticf22 ~]$ ls -F developerworks/ | grep "/$" | sed -e 's/\/$//'
my first article
readme
schema
templates
tools
web
xsl

 [ian@atticf22 ~]$ testfunc () { echo "$# parameters"; echo "$@"; }
 [ian@atticf22 ~]$ testfunc
 0 parameters

 [ian@atticf22 ~]$ testfunc a b c
 3 parameters
 a b c
 [ian@atticf22 ~]$ testfunc a "b c"
 2 parameters
 a b c

[ian@atticf22 ~]$ # You can enter the function on one line
[ian@atticf22 ~]$ ldirs () { ls -F "$@" |  grep "/$" | sed -e 's/\/$//'; }
[ian@atticf22 ~]$ # Or you can enter it on multiple lines
[ian@atticf22 ~]$ # in which case you do not need the final semi-colon
[ian@atticf22 ~]$ ldirs ()
> {
> ls -F "$@" |  grep "/$" |
> sed -e 's/\/$//'
> }

[ian@atticf22 ~]$ ldirs developerworks/ ~/developerworks/xsl/7.0/
my first article
readme
schema
templates
tools
web
xsl
en_US
en_VN
es_AR
ja_JP
ko_KR
pt_BR
ru_RU
zh_CN
[ian@atticf22 ~]$ ldirs -ilrt developerworks
2511035 drwxrwxr-x. 3 ian ian  4096 Mar  5  2013 web
3019425 drwxrwxr-x. 4 ian ian  4096 Sep 12  2014 xsl
2511022 drwxrwxr-x. 3 ian ian  4096 Sep 12  2014 templates
2511036 drwxrwxr-x. 4 ian ian  4096 Sep 12  2014 schema
3023428 drwxrwxr-x. 3 ian ian  4096 Sep 12  2014 tools
3282516 drwxrwxr-x. 2 ian ian  4096 Sep 12  2014 readme
3277408 drwxrwxr-x. 2 ian ian  4096 Nov 13 13:06 my first article
[ian@atticf22 ~]$ ldirs  developerworks/my\ first\ article/
[ian@atticf22 ~]$ mkdir developerworks/my\ first\ article/"dir example"
[ian@atticf22 ~]$ ldirs  developerworks/my\ first\ article/
dir example

[ian@atticf22 ~]$ ls -a /etc/skel/
.  ..  .bash_logout  .bash_profile  .bashrc  .emacs  .kshrc  .mozilla

[ian@atticf22 ~]$ cat /etc/default/useradd
# useradd defaults file
GROUP=100
HOME=/home
INACTIVE=-1
EXPIRE=
SHELL=/bin/bash
SKEL=/etc/skel
CREATE_MAIL_SPOOL=yes

[ian@atticf22 ~]$ echo $PATH
/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/home/ian/.local/bin:/home/ian/bin
[ian@atticf22 ~]$ su -
Password:
[root@atticf22 ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

[ian@atticf22 ~]$ # Augment the path
[ian@atticf22 ~]$ augpath=":$PATH:"
[ian@atticf22 ~]$ # demonstrate with /usr/bin
[ian@atticf22 ~]$ augdir=":/usr/bin:"
[ian@atticf22 ~]$ echo -e "$augdir\n$augpath\n${augpath/$augdir}":/usr/bin:
:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/home/ian/.local/bin:/home/ian/bin:
:/usr/local/bin:/usr/local/sbin/usr/sbin:/bin:/sbin:/home/ian/.local/bin:/home/ian/bin:
[ian@atticf22 ~]$ test "$augpath" != "${augpath/$augdir}" && echo Found || echo Not
Found

[ian@atticf22 ~]$ add2path ()
> {
> local augpath augdir
> augpath=":$PATH:"
> augdir=":$1:"
> test "$augpath" = "${augpath/$augdir}" && PATH="$1:$PATH"
> }
[ian@atticf22 ~]$ add2path /opt/company-bin
[ian@atticf22 ~]$ echo $PATH
/opt/company-bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:
   /sbin:/home/ian/.local/bin:/home/ian/bin

 [ian@atticf22 ~]$ cat /etc/profile.d/company-dir.sh
 # Declare the add2path function

 add2path ()
 {
    local augpath augdir
    augpath=":$PATH:"
    augdir=":$1:"
    test "$augpath" = "${augpath/$augdir}" && PATH="$1:$PATH"
 }

 # Add /opt/company-bin if not already on non-root PATH
 [ $(id -u) -ne 0 ] && add2path /opt/company-bin