Remove certain characters from char*

Question 1

I've got an array of char* with serial data that I'm trying to remove ':' from. I have tried to iterate through the char*, find and remove any colons but it just comes out as garbage.

  char* espData[15];  // pull data from serial and tokenize with strtok > feed to espData  for(int x = 0; x < index-1; x++){    size_t nullTerm = strlen(espData[x]);    espData[x][nullTerm - 1] = '\0';    char* output    for(size_t i = 0; i < strlen(espData[x]); ++i){      if(espData[x][i] != ':') output += espData[x][i];    }    espData[x] = output;    Serial.println(espData[x]);  }

Moving the null character works fine (I wanted to get rid of the last character in every string). Most of the answers I found for general C++ used std::string which we don't have access to.

Question 2

Arithmetic on achar* does nothing to its contents.

Question 3

the commenttokenize with strtok suggests your code uses strtok, which would be one (probably bloated) solution - yet your code doesn't use strtok!!?

Question 4

espData[x][nullTerm - 1] = '\0'; is redundant code

Question 5

@Jaromanda Actually, it overwrites the last character in the string - or underflows the buffer ifnullTerm is0!

Question 6

@JohnBurger - of course you're right

Question 7

You've assumed that achar * is some kind of string object, since you've got the following line of code:output += espData[x][i];, and then laterespData[x] = output;

It quite simply doesn't work like that. At best you can pointoutput insideespData[x] and then do some other logic: but your attempt to "accumulate" the correct characters is incorrect.

Please consider the following code instead:

char* espData[15];for(int x = 0; x < index-1; x++){    size_t nullTerm = strlen(espData[x]); // Get current length    char* output = espData[x];            // Start of string    for (size_t i = 0; i < nullTerm; ++i){        if(espData[x][i] != ':') {        // If it's NOT a colon            *output++ = espData[x][i];    // Copy character 'up'        } // if                                          // If it WAS a colon, then                                          // output does NOT get incremented    } // for    *output = '\0'; // End string off with NUL    Serial.println(espData[x]);} // for

Question 8

That works perfectly, thank you! I have never been great with pointers

Question 9

@Tri42 I just finished a pointer-post on another question. Take a look:arduino.stackexchange.com/a/25317/22924

John Burger 1,8851 gold badge14 silver badges24 bronze badges · Accepted Answer · 2016-06-15 11:05:25Z

You've assumed that achar * is some kind of string object, since you've got the following line of code:output += espData[x][i];, and then laterespData[x] = output;

It quite simply doesn't work like that. At best you can pointoutput insideespData[x] and then do some other logic: but your attempt to "accumulate" the correct characters is incorrect.

Please consider the following code instead:

char* espData[15];for(int x = 0; x < index-1; x++){    size_t nullTerm = strlen(espData[x]); // Get current length    char* output = espData[x];            // Start of string    for (size_t i = 0; i < nullTerm; ++i){        if(espData[x][i] != ':') {        // If it's NOT a colon            *output++ = espData[x][i];    // Copy character 'up'        } // if                                          // If it WAS a colon, then                                          // output does NOT get incremented    } // for    *output = '\0'; // End string off with NUL    Serial.println(espData[x]);} // for

That works perfectly, thank you! I have never been great with pointers
@Tri42 I just finished a pointer-post on another question. Take a look:arduino.stackexchange.com/a/25317/22924

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Remove certain characters from char*

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