Example 1: Infinite While loop in a shell script An infinite While loop means your script will run the loop commands non-stop. Infinite While loops never stop running and this occurs when the condition always turns out to be “True.” You can create an infinite While loop with the followin...
Shell while 循环while 循环用于不断执行一系列命令,也用于从输入文件中读取数据;命令通常为测试条件。其格式为:while command do Statement(s) to be executed if command is true done命令执行完毕,控制返回循环顶部,从头开始直至测试条件为假。以下是一个基本的 while 循环,测试条件是:如果 COUNTER 小于5,那么...
breakexits from afor,select,while, oruntilloop in a shell script. Ifnumberis given,breakexits from the given number of enclosing loops. The default value ofnumberis1. Usage Notes This is a special built-in command of the shell. Exit Values breakalways exits with an exit status of0....
In this example, it gets the filename to read, and using exec it redirects stdin to a file. From that point on, all stdin comes from that file, rather than from keyboard. read command reads the line from stdin, so while loop reads the stdin, till EOF occurs. Bash Until Loop The un...
For example, let’s create a Bash script that has an array of 5 elements and print each element using thewhileloop. #!/bin/bash city=("Washington" "New_York" "Texas" "Chicago" "Austin") i=0 while [ $i -lt ${#city[@]} ] ...
There are times when you have a file having thousands of lines but what if you want to count the number of the lines? You can use the while loop in that case: #!/bin/bash filename="example.txt" line_count=0 while IFS= read -r line; do ...
In shell scripting, using user input as a condition for awhileloop adds dynamic executionas it enables us to control the flow of the script based on their input. 3.1. Prompting for User Input To demonstrate, let’s utilize thereadcommand to prompt the user: ...
shell Bash中的While-loop子壳困境问题在于while循环是管道的一部分。在bash管道中，管道的每个元素都在...
Expect for loop example : for {set i 1} {$i < $no} {incr i 1} { set $total [expr $total * $i ] } puts "$total"; Note: You should place the loop open brace in the same line as it contains “for” keyword. Expect While Loop Examples: ...
3. Using a while loop to manipulate a file Another useful application of awhileloop is to combine it with thereadcommand to have access to columns (or fields) quickly from a text file and perform some actions on them. In the following example, you are simply picking the columns from a ...