How to add a character at end of string

Question

I have a file copy program that takes from one file and pastes in another file pointer. But, instead of getting targetname from user input i'd like to just add a '1' at the end of the input filename and save. So, I tried something like this...

       .... header & inits ....
       fp=fopen(argv[1],"r");
       fq=fopen(argv[1].'1',"w");
       .... file copy code ....

Yeah it seems stupid but I'm a beginner and need some help, do respond soon. Thanks :D

P.S. Want it in pure C. I believe the dot operator can work in C++.. or atleast i think.. hmm

One more thing, i'm already aware of strcat function.. If i use it, then i'll have to define the size in the array... hmm. is there no way to do it like fopen(argv[1]+"extra","w")

The `.` operator doesn't concatenate strings in C or C++, it's for member access for things like struct instances. What you're trying to do is concatenate/append strings, see here: http://stackoverflow.com/questions/308695/c-string-concatenation — wkl, Oct 27 '11 at 18:50

score 7 · Accepted Answer · answered Oct 28 '11 at 09:43

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char* stradd(const char* a, const char* b){
    size_t len = strlen(a) + strlen(b);
    char *ret = (char*)malloc(len * sizeof(char) + 1);
    *ret = '\0';
    return strcat(strcat(ret, a) ,b);
}

int main(int argc, char *argv[]){

    char *str = stradd(argv[1], "extra");

    printf("%s\n", str);

    free(str);

    return 0;
}

Morten Kristensen · Answer 2 · 2011-10-27T19:04:35.657

4

Have a look at strcat:

An example:

#include <string.h>
char alpha[14] = "something";
strcat(alpha, " bla"); // "something bla"
printf("%s\n", alpha);

edited Oct 27 '11 at 19:04

answered Oct 27 '11 at 18:50

Morten Kristensen

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The use of beta is superfluous. strcat will essentially put the "bla" in the area left by alpha. Then it will set beta=alpha. you would have as follows: Before: *alpha is "something" after: *alpha is "somethingbla" and beta=alpha – James Matta Oct 27 '11 at 19:01

score 1 · Answer 3 · answered Oct 27 '11 at 18:51

1

Using the dot won't work.

The function you are looking for is called strcat.

answered Oct 27 '11 at 18:51

Dennis

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score 1 · Answer 4 · answered Oct 27 '11 at 18:59

1

Unfortunately . would not work in c++.

A somewhat inelegant but effective method might be to do the following.

int tempLen=strlen(argv[1])+2;
char* newName=(char*)malloc(tempLen*sizeof(char));
strcpy(newName,argv[1]);
strcat(newName,"1");

answered Oct 27 '11 at 18:59

James Matta

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score -3 · Answer 5 · edited Nov 18 '14 at 00:48

-3

In C to concatenate a string use strcat(str2, str1)

strcat(argv[1],"1") will concatenate the strings. Also, single quotes generate literal characters while double quotes generate literal strings. The difference is the null terminator.

edited Nov 18 '14 at 00:48

Zach Saucier

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answered Oct 27 '11 at 18:50

Turcogj

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...but this question is not tagged C++. – Jon Oct 27 '11 at 18:51
Only for strings which have + overloaded. Doing this to chars will add their pointers. – Pubby Oct 27 '11 at 18:53

How to add a character at end of string

5 Answers5