Linux shell get random number

the Shell Profile:
When a new interactive shell is started, /etc/profile, followed by /etc/bash.bashrc(if a
bash shell), ~/.profile, and finally ~/.bashrc are executed in that order.
PATH
You can set your PATHenvironment variable to tell the shell where to search for programs (and scripts)
to be run. The main system commands are in /bin, /usr/bin, /sbin, and /usr/sbin, but you may
have your own scripts in $HOME/bin, $HOME/scripts, /usr/local/bin, or elsewhere. Append these to
the PATHso that they will be found by the shell even when you are not in that directory:
PATH=${PATH}:${HOME}/bin
ls aliases
Because it is such a common command, there are a few popular lsaliases, the two most common
being llfor ls -land lafor ls -a. Your distribution might even set these for you. Some popular
lsaliases include:
# save fingers!
alias l=’ls’
# long listing of ls
alias ll=’ls -l’
# colors and file types
alias lf=’ls -CF’
# sort by filename extension
alias lx=’ls -lXB’
# sort by size
alias lk=’ls -lSr’
# show hidden files
alias la=’ls -A’
# sort by date
alias lt=’ls -ltr’

History:
# append, don’t overwrite the history
shopt -s histappend
# control the size of the history file
export HISTSIZE=100000
export HISTFILESIZE=409600
# ignore common commands
export HISTIGNORE=”:pwd:id:uptime:resize:ls:clear:history:”
# ignore duplicate entries
export HISTCONTROL=ignoredups
history

~/.inputrc and /etc/inputrc
/etc/inputrcand ~/.inputrcare used by GNU readline facility (used by bash and many other
utilities to read a line of text from the terminal) to control how readline behaves.
set completion-ignore-case On

http_proxy = serveraddress
proxy_user = username
proxy_password = password

sample:
echo "My name is  basename $0  - I was called as $0"
echo "I was called with $# parameters."
count=1
while [ "$#" -ge "1" ]; do
echo "Parameter number $count is: $1"
let count=$count+1
shift
done

$ ./manyparams.sh one two three
My name is manyparams.sh - I was called as ./manyparams.sh
I was called with 3 parameters.
Parameter number 1 is: one
Parameter number 2 is: two
Parameter number 3 is: three

生成序列的方法：
seq 10 -1 1
seq 1 1 10
seq last
seq first incr last
seq first last
生成随机数的方法：
$RANDOM
RANDOM produces a random number between 0 and 32767.
if you want to generate data between m...n , write a function
function getrand()
{
MIN=$1
MAX=$2
let "RANGE=$MAX-$MIN";
if [ "$RANGE" -le "0" ]; then
echo "Error - MAX IS LESS THAN MIN"
fi
#(())表示数学运算
return $(($RANDOM % $RANGE +$MIN))
}
getrand 1 1000
#$?表示返回值
echo $?

if 判断中常用的一些表达式：
－d ：判断制定的是否为目录
－z：判断制定的变量是否存在值
－f：判断制定的是否为文件
－L:判断制定的是否为符号链接
－r：判断制定的是否可读
－s:判断存在的对象长度是否为0
－w:判断制定的是否可写
－x：判断存在的对象是否可以执行
！：测试条件的否定符号

time format
 echo $(date "+%Y%m%d %H:%M:%S")

IFS
IFS is the Internal Field Separator: It lists the set of characters that may be used as whitespace. Its
default value is <space><tab><newline>
IFS=$(echo )