c++ - find first file in directory on linux system?

[BabaG]

all the examples i've seen seem to be for windows and are a
bit different than what i need. also, findfirstfile is not
in the textbook i bought to use as reference.

i need to find the first file in a directory so i can perform
a loop for processing. all of the files in the directory will
be of the same type and have the same name except that each
file is numbered. if i can find the first file in the directory,
i should be able to parse the name and increment the numbers in
the loop to move through the directory.

any tips on finding the first file's name?

thanks,
BabaG

[Plasmator]

[open/close]dir and readdir from glibc should do the trick.

[BabaG]

thanks plasmator. found this in searches based off your link:

/* print files in current directory in reverse order */

#include <dirent.h>

main(){

    struct dirent **namelist;

    int n;

    n = scandir(".", &namelist, 0, alphasort); 

    if (n < 0) 
        perror("scandir"); 
    else { 

        while(n--) { 
            printf("%s\n", namelist[n]->d_name); 
            free(namelist[n]); 
        } 

        free(namelist); 
    } 
}

does almost exactly what i need so i think i can adapt
it if i can get this working. it produces errors when
i compile it. i get:

perror was not declared in this scope
printf was not declared in this scope
free was not declared in this scope
free was not declared in this scope

how do i properly declare these? or do i simply have
the wrong commands there for c++?

thanks,
BabaG

[Paul McKenzie]

thanks plasmator. found this in searches based off your link:

/* print files in current directory in reverse order */

#include <dirent.h>

main(){

    struct dirent **namelist;

    int n;

    n = scandir(".", &namelist, 0, alphasort); 

    if (n < 0) 
        perror("scandir"); 
    else { 

        while(n--) { 
            printf("%s\n", namelist[n]->d_name); 
            free(namelist[n]); 
        } 

        free(namelist); 
    } 
}

does almost exactly what i need so i think i can adapt
it if i can get this working. it produces errors when
i compile it. i get:

perror was not declared in this scope
printf was not declared in this scope
free was not declared in this scope
free was not declared in this scope

how do i properly declare these? or do i simply have
the wrong commands there for c++?

thanks,
BabaG

The code you found is for 'C' compilers.

The code will not compile for C++ for various reasons. First, In C++, all functions must be declared or defined before using them. You just can't call printf() without it being declared. You are missing the <cstdio> header. You are also missing the headers that declare perror() and free().

Second, the main() function returns an int.

int main()

All you have is main().

Regards,

Paul McKenzie

[BabaG]

thanks paul.

added:

#include <cstdio>
int main()
return 0

and am now left with only:

free was not declared in this scope
free was not declared in this scope

how do i declare 'free'?

thanks again,
BabaG

[laserlight]

#include <cstdlib> for free().

[BabaG]

thanks!