Test: Difference between revisions

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When comparing strings in Bash you can use the following operators:
When comparing strings in Bash you can use the following operators:


<b>Equals/Not Equals:</b>
<code>string1 = string2</code> and <code>string1 == string2</code> - The equality operator returns true if the operands are equal.
<code>string1 = string2</code> and <code>string1 == string2</code> - The equality operator returns true if the operands are equal.


- Use the = operator with the test [ command.<br />
- Use the = operator with the test [ command.<br />
- Use the == operator with the [[ command for pattern matching.
- Use the == operator with the [[ command..
 
string1 != string2 - The inequality operator returns true if the operands are not equal.
 
 
<b>Regex Match:</b>
string1 =~ regex- The regex operator returns true if the left operand matches the extended regular expression on the right.
 
 
<b>Greater than/Less than:</b>
string1 > string2 - The greater than operator returns true if the left operand is greater than the right sorted by lexicographical (alphabetical) order.
 
string1 < string2 - The less than operator returns true if the right operand is greater than the right sorted by lexicographical (alphabetical) order.
 


    string1 != string2 - The inequality operator returns true if the operands are not equal.
<b>String Length:</b>
    string1 =~ regex- The regex operator returns true if the left operand matches the extended regular expression on the right.
-z string - True if the string length is zero.<br />
    string1 > string2 - The greater than operator returns true if the left operand is greater than the right sorted by lexicographical (alphabetical) order.
-n string - True if the string length is non-zero.
    string1 < string2 - The less than operator returns true if the right operand is greater than the right sorted by lexicographical (alphabetical) order.
    -z string - True if the string length is zero.
    -n string - True if the string length is non-zero.




<b>Note:</b>
<b>Note:</b>


- A blank space must be used between the binary operator and the operands.
- A blank space must be used between the binary operator and the operands.<br />
- Always use double quotes around the variable names to avoid any word splitting or globbing issues.
- Always use double quotes around the variable names to avoid any word splitting or globbing issues.

Latest revision as of 18:53, 6 May 2019

The test command (or [[ ]]) is used to test various conditions, or to compare strings.


When comparing strings in Bash you can use the following operators:


Equals/Not Equals: string1 = string2 and string1 == string2 - The equality operator returns true if the operands are equal.

- Use the = operator with the test [ command.
- Use the == operator with the [[ command..

string1 != string2 - The inequality operator returns true if the operands are not equal.


Regex Match: string1 =~ regex- The regex operator returns true if the left operand matches the extended regular expression on the right.


Greater than/Less than: string1 > string2 - The greater than operator returns true if the left operand is greater than the right sorted by lexicographical (alphabetical) order.

string1 < string2 - The less than operator returns true if the right operand is greater than the right sorted by lexicographical (alphabetical) order.


String Length: -z string - True if the string length is zero.
-n string - True if the string length is non-zero.


Note:

- A blank space must be used between the binary operator and the operands.
- Always use double quotes around the variable names to avoid any word splitting or globbing issues.