libssh2_sftp_read man page
libssh2_sftp_read — read data from an SFTP handle
#include <libssh2.h> #include <libssh2_sftp.h>
ssize_t libssh2_sftp_read(LIBSSH2_SFTP_HANDLE *handle, char *buffer, size_t buffer_maxlen);
handle is the SFTP File Handle as returned by libssh2_sftp_open_ex(3)
buffer is a pointer to a pre-allocated buffer of at least
buffer_maxlen bytes to read data into.
Reads a block of data from an LIBSSH2_SFTP_HANDLE. This method is modelled after the POSIX read(2) function and uses the same calling semantics. libssh2_sftp_read(3) will attempt to read as much as possible however it may not fill all of buffer if the file pointer reaches the end or if further reads would cause the socket to block.
Number of bytes actually populated into buffer, or negative on failure. It returns LIBSSH2_ERROR_EAGAIN when it would otherwise block. While LIBSSH2_ERROR_EAGAIN is a negative number, it isn't really a failure per se.
LIBSSH2_ERROR_ALLOC - An internal memory allocation call failed.
LIBSSH2_ERROR_SOCKET_SEND - Unable to send data on socket.
LIBSSH2_ERROR_SFTP_PROTOCOL - An invalid SFTP protocol response was received on the socket, or an SFTP operation caused an errorcode to be returned by the server.