CODEWITHSUNDEEP
csystem-calls
Don Fanucci
Don Fanucci

Reputation: 177

success of lseek system call in c

A small question about lseek (C system call). I know that upon failure the return value of the function will be negative. Can we know for sure that if the return value is not negative the function actually moved to the desired location?

Upvotes: 2

Views: 512

Answers (1)

ikegami
ikegami

Reputation: 386676

If the value is (off_t)-1, there was an error.

If the value isn't (off_t)-1, the call was successful.

From my system's man page,

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.

There are mentions that off_t must be a signed type, so it appear safe to check if the result is negative or non-negative.

Upvotes: 2

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