Checking the exit status using an ‘if’ statement in Bash Using a “if” statement and the “$?” variable, we can determine whether a command or script has executed successfully. Which holds the exit status of the most recent command executed, the syntax of the “if” statement for dete...
How to do string comparison and check if a string equals to a value? How to check if a string is in an array? How to use the Bash ternary operator? How to negate an if condition in a Bash if statement? (if not command or if not equal) How to use the BASH_REMATCH variable with...
The uses of the “-z” and “-n” option to test the string values using the “if” statement in Bash are shown in this tutorial. Using the “If -Z” Statement Sometimes, it is required to check if a string variable is empty or if it contains a string of zero length. There are...
The syntax of a POSIX shell function is fn_name () compound-command [ redirections ], and an alternative syntax in bash is function fn_name [()] compound-command [ redirections ]. A bash compound command is any of the bash if statement and other conditional constructs, bash loops construct...
Chapter 11. Introduction to Shell Scripts(第 11 章 Shell 脚本简介 Shell 脚本简介) If you can enter commands into the shell, you can write shell scripts (also known as Bourne shell scripts). A shell script is a series of commands written in a file; the shell reads the commands from the...
Bash case statements are powerful yet easy to write. When you revisit an old Linux script you'll be glad you used a case statement instead of a long if-then-else statement. The case Statement Most programming languages have their version of a switch or case statement. These direct the flow...
For both directives, if the condition following the “if statement” is false, the preprocessor does not pass any of the program text between the #if and the next #endif to the compiler. If you plan to look at any C code, you’d better get used to this. 条件语句。你可以使用#ifdef...
There are two different ways to declare a bash function: 1. The most widely used format is: <functionname>(){ <commands> } Alternatively, the same function can be one line: <functionname>(){ <commands>; } 2. The alternative way to write a bash function is using the reserved wordfunc...
The following If Then Else statement evaluates whether the $resourceGroup variable has been set. If yes, it returns the value of the variable. If no, it sets the variable. Azure CLI Copy if [ $resourceGroup != '' ]; then echo $resourceGroup else resourceGroup="msdocs-learn-bash-$...
In this example, we have an arraynumberswith five elements. We use a ‘for’ loop to iterate through each element in the array. Inside the loop, we have a conditional ‘if’ statement that checks if the current number is even or odd (using the modulus operator%). Depending on the resu...