Thread: Array of Const Char

Hello, I have been trying to generate array of Const Char but I couldnt make it work. In my program, I wanna do the following:

Ask the user the number of inputs (channels)
Then save each input into an array of Const Char
Also the program will add a string in front of each input

For example:
enter the number of inputs: 3
enter input 1 : 0
enter input 2 : 12
enter input 3 : 3

Code:

const char physicalChannel[Number of Inputs][2]

from these inputs I want to obtain:
physicalChannel[0]="Dev/ai0"
physicalChannel[1]="Dev/ai12"
physicalChannel[2]="Dev/ai3"

I did the following but it didnt work:

#include <stdio.h>

Code:

int main(void)
{
  int d;
  int ChnCount =3;
  const char physicalChannel[ChnCount][2];  
  
	for (d=0; d<ChnCount; d++)
  	{
	printf(" Enter the ID no. (0 to 7) for channel %d of %d: ",d+1, ChnCount);   /*------------*/
	scanf("Dev/ai%s", &physicalChannel[d]); 
	}


  for(d = 0;d < ChnCount;++d)
  {
	printf ("%s \n", physicalChannel[d]);
  }
 
  return 0;
}

Can you please help me with this?

Thanks a lot for your replies. The above code did not work as well. What I want is quite simple but I cannot sort it out for some reason.

The short code I write here is a part of another code. The original data acquisition code requires use of a "for loop". Therefore, I have to input arrays of string through ''for'' loop.
Also, physicalChannel is defined as ''const char''

I wanna define the following via a user input.

physicalChannel[0]="Dev/ai0"
physicalChannel[1]="Dev/ai12"
physicalChannel[2]="Dev/ai3"

Can anyone tell/show me how to do this please?

thanks

Hi again, the following works. But I have to write the whole string i.e.: I type "Dev/ai22". Instead, I only want to type 22 and obtain Dev/ai22. Any solution to this please?

Code:

#include <stdio.h>#include <string.h>


int main(void)
{
  int d;
  int ChnCount =2;
   const char physicalChannel[ChnCount][12];


  
	for (d=0; d<ChnCount; d++)
  	{
	printf(" Enter the ID no. (0 to 39) for channel %d of %d, Add 'Dev1/ai' in front of each ID: ",d+1, ChnCount);   /*------------*/
	scanf("%s", &physicalChannel[d]); 
	}


  for(d = 0;d < ChnCount;++d)
  {
	printf ("%s \n", physicalChannel[d]);
  }
 
  return 0;
}

Okay you say you want the user to only enter the numeric suffix so why not something like:

Code:

#include <stdio.h>
#include <string.h>
 
 
int main(void)
{
    int d;
    const int ChnCount = 2;  // Note the const to avoid VLA issues.
    char physicalChannel[ChnCount][12];
    int number;

    for (d = 0; d < ChnCount; d++)
    {
        printf(" Enter the ID no. (0 to 39) for channel %d of %d: ",d+1, ChnCount);   /*------------*/
        scanf("%d", &number);
        sprintf(physicalChannel[d], "Dev1/a%d", number); 
    }
 
 
  for(d = 0; d < ChnCount; ++d)
  {
    printf ("%s \n", physicalChannel[d]);
  }
  
  return 0;
}

You may want to validate the number before you insert it into your string to insure it is a valid channel.

Jim

Thanks a lot for your replies. The last code gives my my desired output. I have one question remaining.

I am programming a data acquisition device in C. So my code includes the library of this device as well. In reference help of this device tells me that:

Code:

int32 DAQmxCreateAIVoltageChan (TaskHandle taskHandle, const char physicalChannel[], const char nameToAssignToChannel[], int32 terminalConfig, float64 minVal, float64 maxVal, int32 units, const char customScaleName[]);

so physicalChannel is defined as "const char". Does it really matter if I define physicalChannel as "char" just like you defined above?

Originally Posted by cyln

... so physicalChannel is defined as "const char". Does it really matter if I define physicalChannel as "char" just like you defined above?

This is perfectly fine. The const parameter means that the function should not be modifying the data pointed to. The type in the caller does not need to be const.