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e
Joined: 02 Feb 2005
Posts: 9
Location: New York City
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| strcat pointer question |
 Posted: Wed Mar 22, 2006 4:43 pm |
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hi, still learning pointers - can someone explain how to use strcat() to append a single character?
| Code: | | strcat(stringA, stringB[i]); |
doesn't work b/c compiler expects pointer, not a single char at index i.
i tried things like
| Code: | | strcat(stringA, &stringB[i]); |
but i still get "Previous identifier must be a pointer" error. setting a pointer variable first:
| Code: | char *c;
c = &stringB[i];
strcat(stringA, c); |
also doesn't work.
thanks. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Mar 22, 2006 4:59 pm |
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To append a single character which is extracted from another string,
you can use strncat() as shown below.
The program below displays:
Also, we don't normally use "c" as a variable name for a pointer.
"c" is used for a character variable. A generic temporary pointer
is usually called "ptr".
| Code: | #include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#include <string.h>
//============================
void main()
{
char stringA[20] = {"Hello"};
char stringB[27] = {"ABCDEFGHIJKLMNOPQRSTUVWXYZ"};
char *ptr;
int i;
i = 4;
ptr = &stringB[i];
strncat(stringA, ptr, 1);
printf("%s\n\r", stringA);
while(1);
} |
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Guest
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| Posted: Thu Mar 23, 2006 6:28 pm |
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thanks for the quick reply. i didn't see strncat in my manual, that is useful. as it turns out, the error i was getting was due to my passing a string parameter incorrectly. but you are right, i also needed str<b>n</b>cat because i wanted only 1 char. i was confused initally because passing a string name works the same as pointer to that string, but doesn't work in functions like strcat.
| Code: |
void displayString(char string) {
printf("%s", string);
}
//works the same as:
void displayString(char *string_ptr) {
printf("%s", string_ptr);
}
void main() {
char s[6];
char text[6] = "hello";
strcpy(s, text);
displayString(s);
// ...
}
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but the first routine does not work with strcat because it expects a pointer. i thought the reference 'string' was the equivalent to a pointer to the first char in the string array. which i think it is, so i'm a still bit confused. |
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e
Joined: 02 Feb 2005
Posts: 9
Location: New York City
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| Posted: Thu Mar 23, 2006 6:30 pm |
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that was me ('e'), forum logged me out. to clarify:
| Code: |
char string2[7] = " there";
void displayString(char string) {
strcat(string, string2); // *compiler ERROR for this line*
printf("%s", string); // ...but this works (by itself)!
}
//works the same as:
void displayString(char *string_ptr) {
strcat(string_ptr, string2); // this works
printf("%s", string_ptr);
}
void main() {
char s[6];
char text[6] = "hello";
strcpy(s, text);
displayString(s);
// ...
} |
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