Remove first char from received buffer

Question

I have a message which I receive in the rmsg variable. If the first character in this buffer is '1', I want to remove this char and send the rest of the message.

So is there any way to do something like this:

if(rmsg[0]=='1')

//remove the first character in rmsg
strncpy(newbuf,rmsg,rmsglen)

If this is not the right direction could anyone show me how?

just to be clear? You need to remove the first char, then send the new string? — Haris, Aug 27 '15 at 12:35
To clarify more, are you going to use the string (with the first character removed) after sending it? — Some programmer dude, Aug 27 '15 at 12:39
`'1'` is not a string, but a `char`. These are very different datatypes in C and any other language. Using the correct terms will help others to understand what you ask. — too honest for this site, Aug 27 '15 at 12:40

mtszkw · Answer 1 · 2015-08-27T12:44:25.713

I suppose it is what you want to achieve in this case:

if (rmsg[0] == '1') 
    memmove(rmsg, rmsg+1, strlen(rmsg));

Here, after using memmove() function like I posted above, your rmsg string will contain its previous content without first char (which is == '1'), so now you can just send it easily wherever you want.

Live demo: http://ideone.com/1dJjAn
More about memmove() func: http://www.cplusplus.com/reference/cstring/memmove/

score 2 · Answer 2 · answered Aug 27 '15 at 12:36

2

You can use the second char as base address for sending and decrease the length by 1:

   if (rmsglen > 0 && rmsg[0]=='1')
      send (&rmsg[1], rmsglen-1);

answered Aug 27 '15 at 12:36

thumbmunkeys

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ameyCU · Answer 3 · 2015-08-27T12:56:38.260

2

If you want to copy the string to new string expect the first character you can do something like this -

char rmsg[]="1 I can go";
char *newbuf;
newbuf=malloc(strlen(msg));
if(rmsg[0]=='1')
{
    strncpy(newbuf,&rmsg[1],rmsglen-1);  
}
free(newbuf);

Small example -https://ideone.com/IotuBy

edited Aug 27 '15 at 12:56

answered Aug 27 '15 at 12:48

ameyCU

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A couple of thoughts: The `+1` isn't needed since the copied string will be shorter and there's thus enough space for the trailing NULL. Why do you think there's a space after the `1`? And why do you think OP want's to skip it, he doesn't say so? Also, [avoid `strcpy`](http://stackoverflow.com/questions/1258550/why-should-you-use-strncpy-instead-of-strcpy), the length is already known (`rmsglen`). – DarkDust Aug 27 '15 at 12:52
@DarkDust The space after `1` was just my thought in case if it is there. And about `+1` yes that was not needed. And I didn't notice `rmsglen` thus didn't took that in account. But thanks for your input I edited my answer. – ameyCU Aug 27 '15 at 12:58

Remove first char from received buffer

3 Answers3