# _CP_readnext

_CP_readnext is equivalent to the `readnext *result*,*value* from *list*` BASIC statement.

## Syntax

```
 int _CP_readnext(CPSTR** result, int* list, int* value, int expression)
```

 If expression is nonzero, then the secondary list is assumed. The
 _CP_readnext call must be preceded by a _CP_select call
 or a _CP_execute call, which produces an external select list. In the case of
 an external list generated by a _CP_execute, the user should pass a pointer
 to an int containing -1 as the list parameter when readnext is first
 called.

## Description

This function returns -1 if an error occurs. The error code is contained in
 _CP_errno. This situation occurs when there are no more items in the list.
 In this case, _CP_errno will contain PE_END_LIST.

 Tip: When possible, the user should use _CP_select on a file
 rather than a _CP_execute of a TCL select command as the
 _CP_select call is much more efficient.

## Example(s)

```

 /* Prints the first file name in the current account. */

 CPSTR * s = _CP_mkstr("select md with a1 \"d]\" sampling 1");
 CPSTR * id = _CP_str_null;
 int sl = -1;

 _CP_execute(_CP_EXECUTE, s, (CPSTR**) 0, (CPSTR**) 0);
 _CP_readnext(&id, &sl, (int*) 0, 0);
 _CP_print(id);

 /* The following example prints the item names in "myfile". */

 CPSTR * n = _CP_mkstr("myfile");
 CPSTR * id = _CP_str_null;
 int sl = -1;
 int f = -1;

 _CP_open(&f, _CP_str_null, n);
 _CP_select(f, &sl, 0);
 while (_CP_readnext(&id, &sl, (int*) 0, 0) >= 0)
 _CP_print(id);
```

## See also

- [C functions overview](https://d3codex.com/cfunctions/c-functions-overview/)
- [_CP_execute](https://d3codex.com/cfunctions/cp-execute/)
- [_CP_select](https://d3codex.com/cfunctions/cp-select/)

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Source: https://d3codex.com/cfunctions/cp-readnext/ - part of the D3Codex reference.