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What happens if condition is false in Bash while loop?
The condition is evaluated before executing the commands. If the condition evaluates to true, commands are executed. Otherwise, if the condition evaluates to false, the loop is terminated, and the program control will be passed to the command that follows.
How does the while statement in Bash work?
The Bash while loop takes the following form: The while statement starts with the while keyword, followed by the conditional expression. The condition is evaluated before executing the commands. If the condition evaluates to true, commands are executed.
Can you write an infinite loop in Bash?
H ow do I write an infinite loop in Bash script under Linux or UNIX like operating systems? An infinite loop is nothing but a sequence of instructions which loops endlessly, either due to the loop having no terminating condition, having one that can never be met, or one that causes the loop to start over.
Is the break condition of a loop always infinite?
Also, I’m not clear on if this is intentional or not, but the break condition of your loop in general is based on the exit code of the subshell, which in turn will be the exit code of echo, which will always succeed, so the loop in general is infinite. You can see this by replacing false in one of the above with an echo:
How to test if a port is open from a shell script?
If parametrizing the host and port, be sure to specify them as $ {HOST} and $ {PORT} as is above. Do not specify them merely as $HOST and $PORT, i.e. without the braces; it won’t work in this case.
When to use read or while loop in Bash?
The while loop will run until the last line is read. When reading file line by line, always use read with the -r option to prevent backslash from acting as an escape character. By default, the read command trims the leading/trailing whitespace characters (spaces and tabs). Use the IFS= option before read to prevent this behavior:
What happens if there is a connection failure in Bash?
If bash gets a connection failure prior to the specified timeout, then bash will exit with an exit code of 1 which timeout will also return. And if bash isn’t able to establish a connection and the specified timeout expires, then timeout will kill bash and exit with a status of 124.