National Instruments 320682C

Chapter 2 Formatting and I/O Library

String with Comma-Separated ASCII Numbers to Real Array

char *s;

int n;

double a[5]; /* 5 8-byte real numbers */

s = "12.3, 45, 6.5, -1.3E-2, 4";

n = Scan (s, "%s>%5f[x]", a);

/* result: a[0] = 12.3, a[1] = 45.0, a[2] = 6.5, */

/* a[3] = -0.013, a[4] = 4.0, n = 1 */

Remarks

The x modifier causes the comma separators to be discarded.

Scan considers an array target to be satisfied when at least one element of the array is filled in.

If the source string in this example were 12.3, only the first element of a would be filled in, the

other elements would remain unmodified, and Scan would return 1.

Scanning Strings That Are Not NUL-Terminated

int bd;

double x;

char s[20];

ibrd (bd, s, 15);

Scan (s, "%s[w*]>%f", ibcnt, &x);

Remarks

All of the previous examples assume that s is a NUL-terminated string. However, when reading

data from programmable instruments using the GPIB and RS-232 Library functions, the data

transferred is not NUL-terminated. This example uses ibrd to read up to 15 B from a GPIB

instrument. The global variable ibcnt contains the actual number of bytes transferred. Scan

uses the value in ibcnt in conjunction with the w modifier to specify the width of the source

string.

For example, if ibcnt is 12, the format string is interpreted as %s[w12]>%f, causing Scan to

use only the first 12 bytes of s.

The following example is an alternative method for handling strings that are not

NUL-terminated:

int bd;

double x;

char s[20];

ibrd (bd, s, 15);

s[15] = 0; /* ASCII NUL is 0 */

Scan (s, "%s>%f", &x);