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cfilestructdirectory
Joe Kur
Joe Kur

Reputation: 47

C: get first character of d_name

Just wondering, given the following code code snippet 

#include    <stdio.h>
#include    <sys/types.h>
#include    <dirent.h>

void do_ls(char []);

main(int ac, char *av[])
{
    if ( ac == 1 )
        do_ls( "." );
    else
        while ( --ac ){
            printf("%s:\n", *++av );
            do_ls( *av );
    }
}

void do_ls( char dirname[] )



{
    DIR     *dir_ptr;       /* the directory */
    struct dirent   *direntp;       /* each entry    */

    if ( ( dir_ptr = opendir( dirname ) ) == NULL )
        fprintf(stderr,"ls1: cannot open %s\n", dirname);
    else
     {
        while ( ( direntp = readdir( dir_ptr ) ) != NULL )
            printf("%s\n", direntp->d_name[0] );
        closedir(dir_ptr);
    }
}

Instead of getting the whole name of each entry, how do I get a specific character of each entry (for example the first character in the name) instead of the whole name. In the code I tried to use direntp->d_name[0] but it didn't work.

Any help/tips would be greatly appreciated.

Upvotes: 1

Views: 1652

Answers (2)

alk
alk

Reputation: 70911

Change this:

printf("%s\n", direntp->d_name[0] );

to be

printf("%c\n", direntp->d_name[0]);

From the C11 Standard (draft):

7.21.6.1 The fprintf function

[...]

8 The conversion specifiers and their meanings are:

c [...] the int argument is converted to an unsigned char, and the resulting character is written. [...]

s [...] the argument shall be a pointer to the initial element of an array of character type.280) Characters from the array are written up to (but not including) the terminating null character. [...]

Upvotes: 0

Junius L
Junius L

Reputation: 16122

Change the %s to %c in your printf, this will print a character.

#include    <stdio.h>
#include    <sys/types.h>
#include    <dirent.h>

void do_ls(char []);

int main(int ac, char *av[])
{
    if ( ac == 1 )
        do_ls( "." );
    else {
        while ( --ac ) {
            printf("%s:\n", *++av );
            do_ls( *av );
        }
    }
    return 0;
}

void do_ls( char dirname[] )
{
    DIR     *dir_ptr;       /* the directory */
    struct dirent   *direntp;       /* each entry    */

    if ( ( dir_ptr = opendir( dirname ) ) == NULL )
        fprintf(stderr,"ls1: cannot open %s\n", dirname);
    else
    {
        while ( ( direntp = readdir( dir_ptr ) ) != NULL )
            printf("%c\n", direntp->d_name[0] );
        closedir(dir_ptr);
    }
}

Upvotes: 1

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