What is the use of Lseek?

lseek() lets you specify new file offsets past the current end of the file. If data is written at such a point, read operations in the gap between this data and the old end of the file will return bytes containing binary zeros (or bytes containing blanks in the QSYS. LIB and independent ASP QSYS.

What is Lseek in Unix?

The lseek() function allows the file offset to be set beyond the end of the file (but this does not change the size of the file). If data is later written at this point, subsequent reads of the data in the gap (a “hole”) return null bytes (‘\0’) until data is actually written into the gap.

What happens when a user calls lseek system call?

lseek() system call repositions the read/write file offset i.e., it changes the positions of the read/write pointer within the file. In every file any read or write operations happen at the position pointed to by the pointer. lseek() system call helps us to manage the position of this pointer within a file.

What is the return value of Lseek?

RETURN VALUE top Upon successful completion, lseek() returns the resulting offset location as measured in bytes from the beginning of the file. On error, the value (off_t) -1 is returned and errno is set to indicate the error.

How can you find the size of the file using lseek () system call?

int fd = open(filename, O_RDONLY); Now, fd can be passed to ‘lseek()’, instead of the filename. off_t currentPos = lseek(fd, (size_t)0, SEEK_CUR); m->size = lseek(fd, (size_t)0, SEEK_END);

Does Lseek return?

What is a file offset?

An offset into a file is simply the character location within that file, usually starting with 0; thus “offset 240” is actually the 241st byte in the file. See relative address. (3) In word processing, the amount of space a document is printed from the left margin.

What does Fstat return?

fstat() on optical volumes will return the volume capacity or 2,147,483,647, whichever is smaller. The file access time is not changed.

What is offset in Fseek?

fseek() in C/C++ fseek() in C language, is use to move file pointer to a specific position. Offset and stream are the destination of pointer, is given in the function parameters. If successful, it returns zero. If it is not successful, it returns non-zero value.