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Unix system programing device file api

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SwetaLeena1

The document discusses the device file API in Unix systems. It defines device files as interfaces between physical devices like modems and application programs. It explains that mknod is the API used to create device files, which can be block or character special files. Mknod allows programs to interact with devices via device drivers and simplifies programming tasks related to system resources without physical connections. The document provides the prototype and an example of using mknod, specifying the path, permissions, and device ID with major and minor numbers.

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UNIX SYSTEM PROGRAMING SEMINAR-1
NAME- SWETA LEENA USN- 1NH19CS750 SEC-3E Topic :Device file API
Unix system programing device file api
DEVICE FILE API Definition Device files are used to interface physical device(ex:console, modem) with application programs. Modem Device file support is implementation dependent. Unix system provides mknod API to create the Device files. mknod makes block or character special files.
Unix system programing device file api
Why device file It allows application program to interact with a device by device driver. Simplifies many programming tasks. Device files are useful for accessing system resource which have no connections with device.
The prototype of mknod #include<stdio.h> #include<sys/stat.h> #include<unistd.h> int mknod(const char* path_name, mode_t mode, int device_id); Example: mknod(SCSI5,S_IFBLK | S_IRWXU | S_IRWXG | S_IRWXO,(15<<8) | 3); On success mknod API returns 0 , else it returns -1
<sys/stat. h> header defines the structure of the data returned by the functions like stat(),fstat(). The mode specifies the access permission of the files Device id contains the major and minor numbers. The lowest byte of the device_id is set to be minor device number and the next byte is set to be major device number.
Unix system programing device file api
Unix system programing device file api
Unix system programing device file api
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Unix system programing device file api

  • 2. NAME- SWETA LEENA USN- 1NH19CS750 SEC-3E Topic :Device file API
  • 4. DEVICE FILE API Definition Device files are used to interface physical device(ex:console, modem) with application programs. Modem Device file support is implementation dependent. Unix system provides mknod API to create the Device files. mknod makes block or character special files.
  • 6. Why device file It allows application program to interact with a device by device driver. Simplifies many programming tasks. Device files are useful for accessing system resource which have no connections with device.
  • 7. The prototype of mknod #include<stdio.h> #include<sys/stat.h> #include<unistd.h> int mknod(const char* path_name, mode_t mode, int device_id); Example: mknod(SCSI5,S_IFBLK | S_IRWXU | S_IRWXG | S_IRWXO,(15<<8) | 3); On success mknod API returns 0 , else it returns -1
  • 8. <sys/stat. h> header defines the structure of the data returned by the functions like stat(),fstat(). The mode specifies the access permission of the files Device id contains the major and minor numbers. The lowest byte of the device_id is set to be minor device number and the next byte is set to be major device number.