Linux shell script Programming while statement case

1, print the system load every 3 seconds

#!/bin/bashwhiletruedo    uptime    sleep3  Done

2, save the monitoring results to a file, execute in the background, and then monitor the file changes with Tail-f

SH while. sh &[112867

#!/bin/bashwhiletruedo    uptime >> log.txt     Sleep 3  Done

[Email protected]:~/linux/shell/flow_control$Tail-F Log.txt .: -: +Up -Min1User, load Average:0.33,0.35,0.32  .: -: *Up -Min1User, load Average:0.33,0.35,0.32  .: -: -Up -Min1User, load Average:0.31,0.34,0...

3, process scheduling related commands

FG: The current script or task is placed in the foreground for execution. If you specify a task: FG task number. Task number through Jobs query

BG: Put the task in the background to execute

Jobs: View the currently executing script or task

CTRL + Z: Pause execution of current script

SH while1.sh &: Plus &, representing background execution script

[Email protected]:~/linux/shell/flow_control$ FGSH  while.SH^z[1]+ StoppedSH  while.SH[email protected]:~/linux/shell/flow_control$ jobs[1]+ StoppedSH  while.SH[email protected]:~/linux/shell/flow_control$ bg[1]+SH  while.SH&[email protected]:~/linux/shell/flow_control$ jobs[1]+ RunningSH  while.SH&[email protected]:~/linux/shell/flow_control$SH  while.SH&[2]13411[email protected]:~/linux/shell/flow_control$ jobs[1]-RunningSH  while.SH&[2]+ RunningSH  while.SH&[email protected]:~/linux/shell/flow_control$ FGSH  while.SH^z[2]+ StoppedSH  while.SH[email protected]:~/linux/shell/flow_control$ bg[2]+SH  while.SH&[email protected]:~/linux/shell/flow_control$ jobs[1]-RunningSH  while.SH&[2]+ RunningSH  while.SH&

4, print with while loop 0, 1, 2, 3, 4

#!/bin/Bashi=0while5  ]do    echo  $i    ((i + + )) Done

The two brackets can also be

#!/bin/Bashi=0while5  ] "do    Echo  $i    ((i+ + )) Done

You can also use the calculation expression

#!/bin/Bashi=0while5  )The Do    echo  $i    ((i + + )) Done

5, calculate 1 .... 100 of and

[Email protected]:~/linux/shell/flow_control$SH sum.SH 1+2+3.. + -=5050[email protected]:~/linux/shell/flow_control$Cat sum.SH #!/bin/Bashi=1sum=0 while((I <= - )) Do    (( sum=sum+i)) ((I++ )) DoneEcho "1+2+3..+100="${sum}

6, Guess the numbers

#!/usr/bin/Bashsum=$ ((random%Wuyi))Echo "the number you need to guess is:"$sumSleep 1Echo "Please enter a number between 1-50 and start guessing!"Count=0functiontype_num () {Read-P"Please enter a number:"NExpr$n +1&>/dev/NULL    if[$?-ne0]; Then        Echo "Please enter a number"type_numfi}functionguess () {(Count++ ))    if[$n-eq $sum]; Then        Echo "you guessed it, your number is:"${count}if[$count-lt3]; Then            Echo "you're so awesome."        elif[$count-ge3-A $count-lt6]; Then            Echo "It's still good, come on ."        Else            Echo "you got a little water."        fiExit0    elif[$n-GT $sum]; Then        Echo "big guess."type_numElse        Echo "small guess."type_numfi}functionMain () {type_num while true     DoGuess Done}main

Linux shell script Programming while statement case