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(Created page with "The INSTR function searches for the first occurence of a search STRING within a base string and returns the position it was found. {{PageSyntax}} : {{Parameter|position%}} = INSTR([{{Parameter|start%}},] {{Parameter|baseString$}}, {{Parameter|searchString$}}) {{Parameters}} * The optional literal or variable INTEGER {{Parameter|start%}} indicates where in the {{Parameter|baseString$}} the search must start. * The {{Parameter|baseString$}} is a litera...") |
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{{Parameters}} | {{Parameters}} | ||
* The optional literal or variable [[INTEGER]] {{Parameter|start%}} indicates where in the {{Parameter|baseString$}} the search must start. | * The optional literal or variable [[INTEGER]] {{Parameter|start%}} indicates where in the {{Parameter|baseString$}} the search must start. | ||
* The {{Parameter|baseString$}} is a literal or variable [[STRING]] value to be searched for an exact match including [[UCASE$|letter cases]]. | * The {{Parameter|baseString$}} is a literal or variable [[STRING]] value to be searched for an exact match including [[UCASE$|letter cases]]. | ||
* The {{Parameter|searchString$}} is a literal or variable [[STRING]] value being searched. | * The {{Parameter|searchString$}} is a literal or variable [[STRING]] value being searched. | ||
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{{PageDescription}} | {{PageDescription}} | ||
* The function returns the {{Parameter|position%}} in the {{Parameter|baseString$}} where the {{Parameter|searchString$}} was found. | * The function returns the {{Parameter|position%}} in the {{Parameter|baseString$}} where the {{Parameter|searchString$}} was found. | ||
* {{Parameter|position%}} will be 0 if the search found no matches in the base string. | * {{Parameter|position%}} will be 0 if the search found no matches in the base string. | ||
* [[INSTR]] returns 0 if an empty {{Parameter|baseString$}} is passed, and returns 1 with an empty {{Parameter|searchString$}}. | * [[INSTR]] returns 0 if an empty {{Parameter|baseString$}} is passed, and returns 1 with an empty {{Parameter|searchString$}}. | ||
* The {{Parameter|start%}} position is useful when making multiple searches in the same string. See the example below. | * The {{Parameter|start%}} position is useful when making multiple searches in the same string. See the example below. | ||
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{{PageExamples}} | {{PageExamples}} | ||
''Example:'' Reading more than one instance of a word in a string using the INSTR return value as the start value plus 1. | ''Example:'' Reading more than one instance of a word in a string using the INSTR return value as the start value plus 1. | ||
{{CodeStart}} | {{CodeStart}} | ||
text$ = "The cats and dogs where playing, even though dogs don't like cats." | text$ = "The cats and dogs where playing, even though dogs don't like cats." | ||
{{Cl|DO...LOOP|DO}} | {{Cl|DO...LOOP|DO}} | ||
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findmonkey% = {{Cl|INSTR}}(text$, "monkeys") ' find any occurance? | findmonkey% = {{Cl|INSTR}}(text$, "monkeys") ' find any occurance? | ||
PRINT findmonkey%; "'monkeys' were found so it returned:"; findmonkey% | PRINT findmonkey%; "'monkeys' were found so it returned:"; findmonkey% | ||
{{CodeEnd}} | {{CodeEnd}} | ||
{{OutputStart}}There is 'cats' in the string at position: 5 | {{OutputStart}}There is 'cats' in the string at position: 5 | ||
Revision as of 01:50, 23 January 2023
The INSTR function searches for the first occurence of a search STRING within a base string and returns the position it was found.
Syntax
- position% = INSTR([start%,] baseString$, searchString$)
- The optional literal or variable INTEGER start% indicates where in the baseString$ the search must start.
- The baseString$ is a literal or variable STRING value to be searched for an exact match including letter cases.
- The searchString$ is a literal or variable STRING value being searched.
Description
- The function returns the position% in the baseString$ where the searchString$ was found.
- position% will be 0 if the search found no matches in the base string.
- INSTR returns 0 if an empty baseString$ is passed, and returns 1 with an empty searchString$.
- The start% position is useful when making multiple searches in the same string. See the example below.
- The searchString$ should be smaller or equal in length to the baseString$, or 0 is returned.
- Non-zero position% return values can be used as a new start position by adding 1 to re-search the base string. See the example below.
- In a loop, INSTR can search an entire file for occurences of certain words. See the MID$ statement example.
QBasic/QuickBASIC
- The start% position had to be at least 1 or greater when used or there will be an Illegal function call error. In QB64, a start% value of 0 or negative is interpreted as 1 and doesn't generate an error.
Examples
Example: Reading more than one instance of a word in a string using the INSTR return value as the start value plus 1.
text$ = "The cats and dogs where playing, even though dogs don't like cats." DO findcats% = INSTR(findcats% + 1, text$, "cats") ' find another occurance after IF findcats% THEN PRINT "There is 'cats' in the string at position:"; findcats% LOOP UNTIL findcats% = 0 findmonkey% = INSTR(text$, "monkeys") ' find any occurance? PRINT findmonkey%; "'monkeys' were found so it returned:"; findmonkey% |
There is 'cats' in the string at position: 5 There is 'cats' in the string at position: 62 0 'monkeys' were found so INSTR returned: 0 |
- Explanation: When the INSTR return value is 0 there are no more instances of a string in a string so the search loop is exited.
See also