What is in if statement Unix?
Syntax. The if statement executes command and determines if it exited successfully or not. If so, the “consequent” path is followed and the first set of expressions is executed. … The command can be a separate binary or shell script, a shell function or alias, or a variable referencing any of these.
What is $1 in bash script?
$1 is the first command-line argument passed to the shell script. Also, know as Positional parameters. … $0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1)
What is =~?
The =~ operator is a regular expression match operator. This operator is inspired by Perl’s use of the same operator for regular expression matching.
What is in if condition in Linux?
Syntax. This code is just a series of if statements, where each if is part of the else clause of the previous statement. Here statement(s) are executed based on the true condition, if none of the condition is true then else block is executed.
What does fi mean in Linux?
fi statement is the fundamental control statement that allows Shell to make decisions and execute statements conditionally.
What is $? In Unix?
The $? variable represents the exit status of the previous command. Exit status is a numerical value returned by every command upon its completion. … For example, some commands differentiate between kinds of errors and will return various exit values depending on the specific type of failure.
What is S in shell script?
-S filename ] can be read as “not is-socket filename“. So the command is checking whether a “socket” (a special kind of file) exists with each name in the loop. The script uses this command as the argument to an if statement (which can take any command, not just [ ) and sets DOWN to true if any of them does not exist.
What is bash if?
In bash scripting, as in the real world, ‘if’ is used to ask a question. The ‘if’ command will return a yes or no style answer and you can script the appropriate response.
What is E in shell script?
The -e option means “if any pipeline ever ends with a non-zero (‘error’) exit status, terminate the script immediately”. Since grep returns an exit status of 1 when it doesn’t find any match, it can cause -e to terminate the script even when there wasn’t a real “error”.
What is the purpose of in Unix?
Unix is an operating system. It supports multitasking and multi-user functionality. Unix is most widely used in all forms of computing systems such as desktop, laptop, and servers. On Unix, there is a Graphical user interface similar to windows that support easy navigation and support environment.
What is in if condition in shell script?
If specified condition is not true in if part then else part will be execute. To use multiple conditions in one if-else block, then elif keyword is used in shell. If expression1 is true then it executes statement 1 and 2, and this process continues. If none of the condition is true then it processes else part.