Common commands and statements for Shell programming (scripting)

some common shell programming (script) commands and statements can be used to meet general requirements.
command parameters Received:

• Number of parameters:

$#

• Parameter values:

The command itself: $ A first parameter: $ $ ...
Exit Command:Exit
echo Command:

• Line break:

Echo

• No line break after output:

Echo- N"Please select (y/n)?" "

• Output double quotes with escape symbols:

echo "Welcome \" "Official Server \" Deployment Tool. "

• Output with variable:

echo "Upcoming Deployment project:$project _name"

• Output a string with an escape character:

Echo- e"First\ tSecond

• Output to File

Append to end of file: Echo-e $log _info>>Deploy.log Overwrite file contents: Echo-e $log _info>Deploy.log
printf Command: (can replace echo, formatted output, same as printf function in C language)

• Output a number of two digits after the decimal point, and wrap:

printf "The number is%.2f.\ n"100

• Outputs a string of a specified width:

Left-justified: printf "%-20s%-15s%10.2f\n "Stephen" "Liu" 35 right-aligned: printf "|%10s|\n "Hello
variables:

• Defined:

profile= "Production"

• Use:

Echo $ profile

• Variable stitching:

log_info= "$log _info, $target _ip"
array:

• Defined:

servers= ("192.168.0.31" "192.168.0.39")projects= ("Public" "Industry" "Logistics" "misc")

• Get the entire array:

${projects[*]}

• Get the number of array elements:

${#servers [@]}
The IF statement (conditional judgment also applies to the while statement and the For statement):

• Determine if a variable (project) is not empty:

if [ $project];thenecho "Variable \" Project\ "is null." Fi

• Judgment is not equal to:

if [$#-ne3];then echo "command line parameter not 3" fi

• Boolean-Valued Judgment:

if [ "$is _ip_correct" = False ];thenecho "Invalid IP address, please use one of the following IPs:" Echo ${servers[*]} exit fi

• String Equality judgment:

If["$confirm" = = "Y"]&&["$confirm"! = "n"];d o # do something...fi

• Regular expression judgment

if [[$ =~ ^public|industry$]] && [[$ =~ ^[yn]$]];then # do something...fi
If[ [! $deploy _more =~ [yn] ]; then # do something...fi

• Determine if the file exists:

if [!- Ftarget/$project. War];then # do something ...
Fi

• Determine if the directory exists:

if [- D$2/webapps/$1];then # do something...fi

• To determine the suffix of a file name (string)

Backup_file= "/backup/java_data/$1-$today. War" backup_file= "/backup/java_data/$1-$today. Gz"
if ["${backup_file##*.}"= "war"];then CP $backup _file $1.war elif ["${backup_file##*.}"= "GZ"];then tar zxvf $backup _file else echo "backup file format not" Exit fi
Read statement (reads the string entered by the user):

• The simplest usage: Read user input to variable yes_or_no

Read Yes_or_no

• Prompt user to enter Y or n

read-e-P "Do you want to back up: (y/n)? "-I" Y "needbackup(Parameter Description:-e: I do not know what is the use, but if removed, I will fail;-P: followed by the prompt statement;-I: followed by the default input; the last parameter is the variable that holds the user input.))
Select statement (prompting the user to select one from the list):

• Modify the default prompt (the default value is "#?") ）：

ps3="Please select an item:"

• Prompts the user to select a value from the array:

Selectproject in ${projects[*]};d o if [$project];then break FI-Done
or add exit Condition: Select Target_ip in${servers[*]}"Exit (Exit)";d o if [" $target _ip "=" exit (exit) "]; Then echo "Thank you for using!" good-bye! "Break fi
If [$target _ip]; Then # does something fi done
Case Statement:Case $project inPublic )project_name= "Volkswagen Edition";;Logistics)project_name= "Deliveryversion" ;;misc)project_name= "Miscellaneous edition";;Esac
While statement:

• Match regular expressions to determine the use:

while [[! $needbackup =~ ^[yn]$]];d o read-e-P "Backup: (y/n)? "-I" Y "needbackup done

• Make a progress bar with "..."

Echo-n "Wait for the $port port to open ..." while [! $pid _new];d o #sleep 1 pid_new= ' NETSTAT-NLP | grep $port | awk ' {print $7} ' | Awk-f "/" ' {print '} ' echo-n ' ... "done
For statement:

• Traverse:

For ip_t in ${servers[*]};d o If ["$" = "$ip _t"];then is_ip_correct=true break Fidone
Call other programs:

• Use ', and get the output result:

ps3= "Please choose a branch:" Select Branch in' svn list svn://<svn_host>/java/code/branches ';d o if [$branch];then svn_dir= "svn://<svn_host>/java/code/branches/$branch" project_dir=$ Branch break FI-Done

• using $ (), and obtain the output result:

today=$ (Date+%y-%m-%d/%h:%m:%s)svn_version=$(SVN info $SVN _dir | grep "Last Changed Rev:" | awk ' {print $4} ')

• Invoke other programs silently (without outputting results, output to a null device)

RM $2/logs/m* $2/logs/l* $2/logs/h* $2/logs/catalina.2015*&>/dev/null &
awk (used to slice a string, typically with grep):

• Get the fourth string separated by a space:

svn_version=$ (svn info $svn _dir | grep "Last Changed Rev:" |awk ' {print $4} ')

• Gets the first string separated by a special delimiter ("/")

Awk- F "/"' {print '} '

• Get all the port numbers for the $port process and kill

For PID in ' NETSTAT-NLP | grep $port | awk ' {print $7} ' | Awk-f "/" ' {print $} ' do echo ' ==========================warning======================== ' echo ' does not close the process properly, port: $port, Kill directly, Process number: $pid "echo" ==========================warning======================== "Kill $piddone
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Common commands and statements for Shell programming (scripting)