NR | Keyword | Description | Example |
---|---|---|---|
01 | if |
Introduces a conditional statement to execute code based on a condition. | if [ $x -gt 0 ]; then echo "Positive number"; fi (checks if x is positive) |
02 | then |
Follows the if keyword and marks the beginning of the code to execute if the condition is true. |
Refer to if example. |
03 | else |
Provides an optional block of code to execute if the condition in the if statement is false. |
if [ $x -gt 0 ]; then echo "Positive"; else echo "Non-positive"; fi (prints based on x value) |
04 | elif |
Introduces an additional condition to check within an if statement structure. |
if [ $x -gt 0 ]; then echo "Positive"; elif [ $x -lt 0 ]; then echo "Negative"; else echo "Zero"; fi (checks for positive, negative, or zero) |
05 | fi |
Marks the end of an if , else , or elif block. |
Refer to if example. |
06 | case |
Provides a multi-way branching statement based on pattern matching. | case $choice in a) echo "Option A";; b) echo "Option B";; esac (checks the value of choice ) |
07 | esac |
Marks the end of a case statement block. |
Refer to case example. |
08 | for |
Introduces a loop that iterates a set number of times or over a list of items. | for i in {1,2,3}; do echo $i; done (loops from 1 to 3) |
09 | select |
Creates a menu-driven loop for user selection. | select name in John Mary Peter; do echo "Hello, $name!"; break; done (prompts user to choose a name) |
10 | while |
Creates a loop that continues as long as a condition is true. | while [[ $count -lt 5 ]]; do echo $count; count=$((count+1)); done (loops until count reaches 5) |
11 | until |
Creates a loop that continues until a condition becomes true. | until [[ $file -f ]]; do sleep 1; done ; echo "File found!" (loops until file exists) |
12 | do |
Marks the beginning of the code block to be executed within a loop or conditional statement. | Refer to for , while , and until examples. |
13 | done |
Marks the end of the code block for a loop or conditional statement. | Refer to for , while , and until examples. |
14 | in |
Used within loops to specify the list of items to iterate over. | Refer to for example. |
15 | function |
Defines a reusable block of code that can be called with arguments. | function greet { echo "Hello, $1!"; } ; greet World (defines and calls a greeting function) |
16 | time |
Executes a command and reports the elapsed time, user CPU time, and system CPU time used. | time sleep 5 (measures the time spent sleeping for 5 seconds) |
17 | { } |
Delimiters used to define a compound command, which groups multiple commands into a single unit. | { echo "Line 1"; echo "Line 2"; } (groups two echo commands) |
18 | ! |
Logical NOT operator that inverts the truth value of an expression. | if [[ ! $file -e ]]; then echo "File does not exist"; fi (checks if the file doesn't exist) |
19 | [[ ]] |
Provides a more flexible way to write conditional expressions compared to test (brackets). |
Refer to if and while examples using [[ ]] |
Created
March 12, 2024 21:54
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