How do you write an if statement in shell script?
This block will process if specified condition is true. 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.
What is in if condition in shell script?
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.
How do you write an IF command in Linux?
if is a command in Linux which is used to execute commands based on conditions. The ‘if COMMANDS’ list is executed. If its status is zero, then the ‘then COMMANDS’ list is executed.
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)
How do you read a file in shell?
How to Read a File Line By Line in Bash. The input file ( $input ) is the name of the file you need use by the read command. The read command reads the file line by line, assigning each line to the $line bash shell variable. Once all lines are read from the file the bash while loop will stop.
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 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 $# in shell script?
$# is the number of arguments, but remember it will be different in a function. $# is the number of positional parameters passed to the script, shell, or shell function. This is because, while a shell function is running, the positional parameters are temporarily replaced with the arguments to the function.
How do I run a shell script?
Steps to write and execute a script
- Open the terminal. Go to the directory where you want to create your script.
- Create a file with . sh extension.
- Write the script in the file using an editor.
- Make the script executable with command chmod +x <fileName>.
- Run the script using ./<fileName>.
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.
How do I run a bash script?
Make a Bash Script Executable
- 1) Create a new text file with a . sh extension. …
- 2) Add #!/bin/bash to the top of it. This is necessary for the “make it executable” part.
- 3) Add lines that you’d normally type at the command line. …
- 4) At the command line, run chmod u+x YourScriptFileName.sh. …
- 5) Run it whenever you need!