CODEWITHSUNDEEP
clinuxsd-cardmmc
yooo123
yooo123

Reputation: 67

How to create and write to a file on sdcard with linux?

I want to create a file on /dev/mmcblk0, if it doesn't exist already, and then write to it. My question is how to check if there is already such file on the sdcard and then access it, does it show up like /dev/mmcblk0/somefile?

Upvotes: 0

Views: 2239

Answers (2)

Enzo Ferber
Enzo Ferber

Reputation: 3104

You should use the command mount(8) to mount the device first. That will cause the device's filesystem to be attached to your system's file-system, and therefore, makes you able to access files on it just like you normally do. For example:

mount /dev/mmcblk0 /home/yooo123/sdcard

If all goes well, you can read and write files to it using fopen, fwrite, etc. 

FILE *fp = fopen("/home/yooo123/sdcard/file.txt", "w");
...
fprintf(fp, "Hello, SD Card!\n");

However, if you want to do all of that from a C program, look up the mount(2) system call.

int mount(const char *source, const char *target,
      const char *filesystemtype, unsigned long mountflags,
      const void *data);

Upvotes: 1

txk2048
txk2048

Reputation: 321

/dev/mmcblk0 points to a drive, so you will need to mount the drive first before you can see what files are available on it or create new files.

Upvotes: 2

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