READV Section: Linux Programmer's Manual (3) Updated: April 25, 2025 Index   NAME readv, writev - read or write data into multiple buffers   SYNOPSIS #include <sys/uio.h> int readv(int filedes, const struct iovec *vector, size_t count); int writev(int filedes, const struct iovec *vector, size_t count);   DESCRIPTION The readv() function reads count blocks from the file associated with the file descriptor filedes into the multiple buffers described by vector. The writev() function writes at most count blocks described by vector to the file associated with the file descriptor filedes. The pointer vector points to a struct iovec defined in <sys/uio.h> as struct iovect { void *iovbase; /* Starting address */ size_t iov_len; /* Number of bytes */ } ; Buffers are processed in the order vector[0], vector[1], ... vector[count]. The readv() function works just like except that multiple buffers are filled. The writev() function works just like except that multiple buffers are written out.   RETURN VALUES The readv() function returns the number of bytes or -1 on error; the writev() function returns the number of bytes written.   ERRORS The readv() and writev() functions can fail and set errno to the following values: EBADF fd is not a valid file descriptor. EINVAL fd is unsuitable for reading (for readv()) or writing (for writev()). EFAULT buf is outside the processes' address space. EAGAIN Non-blocking I/O had been selected in the open() call, and reading or writing could not be done immediately. EINTR Reading or writing was interrupted before any data was transferred.   CONFORMING TO unknown   BUGS It is not advisable to mix calls to functions like readv() or writev(), which operate on file descriptors, with the functions from the stdio library; the results will be undefined and probably not what you want.   SEE ALSO   Index NAME SYNOPSIS DESCRIPTION RETURN VALUES ERRORS CONFORMING TO BUGS SEE ALSO This document was created by using the manual pages. Time: 11:58:05 GMT, March 24, 2025