Now, we can use $# in our script with a conditional statement to check if $# is equal to zero (meaning no input parameters) to exit if true. If$#$# is greater than 0, the condition becomes false and the else par
Here, we list some basic bash syntax with a brief explanation. It is a good starting point if you are a beginner.
yellow # Multiple arguments can also be passed. $ random_array_element 1 2 3 4 5 6 7 3 1. 2. 3. 4. 5. 6. 7. 循环一个数组 每次printf调用时,都会打印下一个数组元素。当 打印到达最后一个数组元素时,它 再次从第一个元素开始。 arr=(a b c d) cycle() { printf '%s ' "${arr[$...
Check if the numbers are not equal Case 2. The-neoperator checks if integer1 is not equal to integer2. If Integer1 is not equal to integer2, then it returns 0, else it returns 1: [ 10 -ne 20 ] && echo $? || echo $? Check if a number is equal or greater than the other T...
Comparison Operators Comparison operators are used in bash to compare two strings to check if they are equal or not. Here, we will list some comparison operators including, string, and integer operators. Integer Operators Regular Expressions
echo "You are not Alice." fi Example 3: File Check #!/bin/bash file_path="/path/to/file.txt" if [ -f "$file_path" ] then echo "File exists." else echo "File does not exist." fi Compound Condition You can combine multiple conditions using logical operators like && (AND) and ...
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 Regular Expression Operator =~?
Check if string contains a sub-stringUsing a test:if [[ $var == *sub_string* ]]; then printf '%s\n' "sub_string is in var." fi # Inverse (substring not in string). if [[ $var != *sub_string* ]]; then printf '%s\n' "sub_string is not in var." fi # This works ...
Checking if a variable exists ([[ -v varname ]]): Yes, this is possibly a killer argument, but consider the programming style of always setting variables, so you don't need to check if they exist.Are empty string comparisons any special?Of...
-O You are the owner of the file. f1 -nt f2 file f1 is newer than f2. f1 -ot f2 file f1 is older than f2 Comparison Operators Comparison operators are used in bash to compare two strings to check if they are equal or not. Here, we will list some comparison operators including, ...