How to create file inside a directory using C

Question

I am trying to create a directory and a file inside the directory. Below is my code in C, but when I try to compile it, I got this error: invalid operands to binary / (have ‘const char *’ and ‘char *’)

char *directory = "my_dir";

struct stat dir = {0};
if(stat(directory, &dir) == -1)
{
    mkdir(directory, 0755);
    printf("created directory testdir successfully! \n");
}

int filedescriptor = open(directory/"my_log.txt", O_RDWR | O_APPEND | O_CREAT);
if (filedescriptor < 0)
{
    perror("Error creating my_log file\n");
    exit(-1);
}

thanks for help

Answer 1

use sprintf() or similar to create the pathFilename string:

char pathFile[MAX_PATHNAME_LEN];
sprintf(pathFile, "%s\\my_log.txt", directory );

then

int filedescriptor = open(pathFile, O_RDWR | O_APPEND | O_CREAT);   

Note: If you are using linux, change \\ to / and MAX_PATHNAME_LEN to 260 (or whatever linux likes to use for that value.)

EDIT if you need to check that a directory exists before creating a file there, you can do something like this:

if (stat("/dir1/my_dir", &st) == -1) {
    mkdir("/dir1/my_dir", 0700);
}   

Read more here: stat, mkdir

Answer 2

you should do something such as:

char *filepath = malloc(strlen(directory) + strlen("my_log.txt") + 2);
filepath = strcpy(filepath, directory);
filepath = strcat(filepath, "/my_log.txt");

and then use filepath in the open function

Answer 3

Please Refer complete solution:

#include<stdio.h>
#include<string.h>  // for string operations
#include<stdlib.h>  //for malloc()
#include<fcntl.h>   //for creat()
#include<sys/stat.h>    //for struct stat, stat()
#include<unistd.h>  //for close()

int main(int argc,const char **argv)
{
    //variable declaration
    int iFd = 0;
    char *chDirName = NULL;
    char *chFileName = NULL;
    char *chFullPath = NULL;
    struct stat sfileInfo;

    //Argument Validation
    if(argc != 3)
    {
        printf("[ERROR] Insufficient Arguments\n");
        return(-1);
    }

    //argument processing
    chDirName = (char *)malloc(sizeof(char));
    chFileName = (char *)malloc(sizeof(char));
    chFullPath = (char *)malloc(sizeof(char));
    chDirName = strcpy(chDirName,argv[1]);
    chFileName = strcpy(chFileName,argv[2]);

    //create full path of file
    sprintf(chFullPath,"%s/%s",chDirName,chFileName);

    //check directory exists or not
    if(stat(chDirName,&sfileInfo) == -1)
    {
        mkdir(chDirName,0700);
        printf("[INFO] Directory Created: %s\n",chDirName);
    }

    //create file inside given directory
    iFd = creat(chFullPath,0644);

    if(iFd == -1)
    {
        printf("[ERROR] Unable to create file: %s\n",chFullPath);
        free(chDirName);
        free(chFileName);
        free(chFullPath);
        return(-1);
    }

    printf("[INFO] File Created Successfully : %s\n",chFullPath);

    //close resources
    close(iFd);
    free(chDirName);
    free(chFileName);
    free(chFullPath);

    return(0);
}

Run Program With giving two Command Line Arguments:

1. First Argument : DirectoryName
2. Second Argument : FileName

for example : after compiling ./executableName yourFolderName yourFileName