strcat() problems, maybe

This is a discussion on strcat() problems, maybe within the C Programming forums, part of the General Programming Boards category; When I try to cocatenate a character in a buffer to my string, or character array, it gives me the ...

  1. #1
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    strcat() problems, maybe

    When I try to cocatenate a character in a buffer to my string, or character array, it gives me the warning. IT is the line where I am using strcat()
    fdump.c:57: warning: initialization makes pointer from integer without a cast
    here is a snippet of my code that uses this function
    str is a char array
    and buffer is a buffer.

    insert
    Code:
    					for (i=0; i<bytesRead; i++) {
    						if (19<buffer[i]<127]{
    							printf["."];
    						}
    						else{	
    							printf("%s ", buffer[i]);
    						}
    						strcat(str,buffer[i]);
    						bytesPrinted++;

  2. #2
    and the hat of wrongness Salem's Avatar
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    > printf["."];
    How does this even compile?

    And how did you declare str and buffer ?

    buffer[i] sounds like a single char, in which case there are several more mess-ups to deal with as well.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
    ATH0 quzah's Avatar
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    Did you include string.h? Otherwise, is "buffer" a character array? If so, you're doing it wrong. Also, your if check is wrong.


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    and the Hat of Guessing tabstop's Avatar
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    printf["."] doesn't make any sense. strcat(str, buffer[i]) also doesn't make any sense, since you can only add a string to a string and buffer[i] is not a string but a single character. If you need to add a single character to str, then you probably want to do something like
    Code:
    str[some_appropriate_number] = buffer[i]
    and then make sure at the end that str is null-terminated.

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    Quote Originally Posted by tabstop View Post
    printf["."] doesn't make any sense. strcat(str, buffer[i]) also doesn't make any sense, since you can only add a string to a string and buffer[i] is not a string but a single character. If you need to add a single character to str, then you probably want to do something like
    Code:
    str[some_appropriate_number] = buffer[i]
    and then make sure at the end that str is null-terminated.
    Trust me it makes sense in my code.
    And thanks for the help!!

  6. #6
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by cloudsword View Post
    Trust me it makes sense in my code.
    And thanks for the help!!
    If you refer to printing the period, I can only hope that your code actually looks like
    Code:
    printf(".");
    instead of what you posted here.

  7. #7
    ATH0 quzah's Avatar
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    Quote Originally Posted by tabstop View Post
    If you refer to printing the period, I can only hope that your code actually looks like
    I'm guessing they were referring to the buffer[ i ] statement.
    Code:
    char foo[BAR];
    char *baz[BAR];
    ...
    strcat( foo, baz[ i ] );
    It's possible they really did mean ... buffer[ i ].


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  8. #8
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by quzah View Post
    I'm guessing they were referring to the buffer[ i ] statement.
    Code:
    char foo[BAR];
    char *baz[BAR];
    ...
    strcat( foo, baz[ i ] );
    It's possible they really did mean ... buffer[ i ].


    Quzah.
    Then I wish them the best of luck with finding a pointer between 19 and 127.

    Anyway given that the parenthesis in the if statement also mysteriously turned into a bracket I'm guessing it's someone who thinks re-typing the code and introducing strange new errors is cool and cutting-and-pasting the actual code is for losers.

  9. #9
    ATH0 quzah's Avatar
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    Quote Originally Posted by tabstop View Post
    Then I wish them the best of luck with finding a pointer between 19 and 127.
    You mean like this?
    Code:
    char *buf[ 128 ];
    size_t x = 0;
    
    for( x = 0; x < 128; x++ )
    {
        buf[ x ] = malloc( 128 );
        sprintf( buf, "hello number %d!\n", x );
    }
    
    ...on to their code...
    
    strcat( foo, buf[ x ] );
    Something like that? But no, I don't know what they're really meaning to do there either.

    Quzah.
    Hope is the first step on the road to disappointment.

  10. #10
    Guest Sebastiani's Avatar
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    Quote Originally Posted by tabstop View Post
    Then I wish them the best of luck with finding a pointer between 19 and 127.

    Anyway given that the parenthesis in the if statement also mysteriously turned into a bracket I'm guessing it's someone who thinks re-typing the code and introducing strange new errors is cool and cutting-and-pasting the actual code is for losers.
    It never ceases to amaze me how little pertinent information is included in some of these posts. I try to resist the temptation to make references to crystal balls or charades...it's difficult, though.

  11. #11
    Algorithm Dissector iMalc's Avatar
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    Quote Originally Posted by cloudsword View Post
    When I try to cocatenate a character in a buffer to my string, or character array, it gives me the warning. IT is the line where I am using strcat()
    There's your problem right there. You cant use strcat to concatenate a string and a character. You can use it to concatenate a null-terminated string of only one character onto another null-terminated string though. You need to make a null-terminated string of one character somewhere to use strcat.

    You'll get a warning on the printf line too where you're making the same mistake. However , unlike strcat, printf can be used to print a single character, but you need a different format specifier for that: "%c".

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