Cut substring from a String in C

Question

I have a string (ex. "one two three four"). I know that I need to cut word that starts from 4th to 6th symbol. How can I achieve this?

Result should be:

Cut string is "two"
Result string is "one three four"

For now I achieved, that I can get the deleted word - '

for(i = 0; i < stringLength; ++i) { 
          if((i>=wordStart) && (i<=wordEnd))
          {
              deletedWord[j] = sentence[i];
              deletedWord[j+1] = '\0';
              j++;                
          }
    }

but when I fill the sentence[i] = '\0' I have problems with cutting string in the middle.

Some programmer dude · Accepted Answer · 2012-10-14 16:34:37Z

2

Instead of putting '\0' in the middle of the string (which actually terminates the string), copy everything but the word to a temporary string, then copy the temporary string back to the original string overwriting it.

char temp[64] = { '\0' };  /* Adjust the length as needed */

memcpy(temp, sentence, wordStart);
memcpy(temp + wordStart, sentence + wordEnd, stringLength - wordEnd);
strcpy(sentence, temp);

Edit: With memmove (as suggested) you only need one call actually:

/* +1 at end to copy the terminating '\0' */
memmove(sentence + wordStart, sentence + wordEnd, stringLengt - wordEnd + 1);

edited Oct 14, 2012 at 16:34

answered Oct 14, 2012 at 16:06

Some programmer dude

411k36 gold badges420 silver badges655 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

dmckee --- ex-moderator kitten Over a year ago

If your system has memmove there is no need for two copies. Generalizing to the case where the substring to be removed may occur more than once is a fun exercise.

Christoffer Over a year ago

Why not just use memmove(sentence + wordStart, sentence + wordEnd, stringLength - wordEnd)?

divide by zero Over a year ago

Because i need to show "what I have deleted"... I have solved this, will try this with memmove now :) ty

divide by zero Over a year ago

Actually what i need is to delete word by enetered number. and when i wish to delete 1st word from a sentence with 1 word - it failed... trying to solve this.

user411313 Over a year ago

@dmckee: memmove ist C standard (C89), every 'pure C' system must support this

Christoffer · Accepted Answer · 2012-10-14 16:11:08Z

2

When you set a character to '\0' you're terminating the string.

What you want to do is either create a completely new string with the required data, or, if you know precisely where the string comes from and how it's used later, overwrite the cut word with the rest of the string.

answered Oct 14, 2012 at 16:11

Christoffer

13k8 gold badges40 silver badges53 bronze badges

Comments

vrk001 · Accepted Answer · 2012-10-14 16:28:25Z

0

/*sample initialization*/
char sentence[100] = "one two three four";

char deleted_word[100];
char cut_offset = 4;
int cut_len = 3;

/* actual code */
if ( cut_offset < strlen(sentence) && cut_offset + cut_len <= strlen(sentence) )
{
    strncpy( deleted_word, sentence+cut_offset, cut_len);
    deleted_word[cut_len]=0;

    strcpy( sentence + cut_offset, sentence + cut_offset + cut_len);
}

answered Oct 14, 2012 at 16:28

vrk001

3451 gold badge2 silver badges11 bronze badges

Collectives™ on Stack Overflow

Cut substring from a String in C

3 Answers 3

5 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

5 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related