CODEWITHSUNDEEP
cstringfindsubstringsubstr
CodeKingPlusPlus
CodeKingPlusPlus

Reputation: 16081

C string functions

In C, how do I extract the first n characters from a string until I find a space in the string? Essentially, which C function will find the position of the next space for me and which C function will give me a substring? I am thinking in terms of C++. such as:

string str = "Help me Please!";
int blankPos = str.find(' ');
str.substr(0, blankPos);

Thanks,

Upvotes: 1

Views: 6293

Answers (7)

DrMad
DrMad

Reputation: 490

char str[] = "Help me Please";    // Source string
char newstr[80];                  // Result string

// Copy substring characters until you reach ' ' (i.e. "Help")
for (i=0; str[i] != ' '; i++) {
  newstr[i] = str[i];
}
newstr[i] = 0;                    // Add string terminator at the end of substring

Upvotes: 1

Patrick Schlüter
Patrick Schlüter

Reputation: 11871

Another variant allowing to use more than one character as delimitter. 

char str[] = "Help me Please";
char newstr[80]; 

char *p = strpbrk(str, " \t\xA0");   /* space, tab or non-breaking space (assuming western encoding, that part would need adaptation to be trule portable) */
if(p)
  strlcpy(newstr, str, p - str + 1);
else
  newstr[0] = 0;

strlcpy is not standard but widespread enough to be used. If it is not available on the platform, it's easy to implement. Note that strlcpy always puts a 0 at the last position copied, therfore the +1 in the length expression.

Upvotes: 0

Ajai
Ajai

Reputation: 3500

char* str = "Help me Please";
int i =0;

//Find first space
while(str[i] != ' '){
  i++;
}
char* newstr;
newstr = strndup(str+0,i);

I guess you could also use strchr() to get the first space in the string.

Upvotes: 0

Christian Rau
Christian Rau

Reputation: 45968

So you want something like:

#include <string.h>

const char *str = "Help me Please";

//find space charachter or end of string if no space found
char *substr, *space = strchr(str, ' ');
int len = space ? (space-str) : strlen(str);

//create new string and copy data
substr = malloc(len+1);
memcpy(substr, str, len);
substr[len] = 0;

Upvotes: 0

TMN
TMN

Reputation: 3070

If you just want to get the first part of the string, use strchr() as everyone has suggested. If you're looking to break a string into substrings delimited by spaces, then look into strtok().

Upvotes: 0

Fred Foo
Fred Foo

Reputation: 363858

  1. Use strchr to find the space.
  2. Allocate a new char buffer to hold the substring.
  3. Copy the substring into the buffer with memcpy.

Upvotes: 1

Nim
Nim

Reputation: 33655

hint: strchr()

I need to type some more characters.

Upvotes: 1

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