/usr/man/cat.3/BIO_gets.3

BIO_read(3)                  OpenSSL                  BIO_read(3)

NAME

     BIO_read, BIO_write, BIO_gets, BIO_puts - BIO I/O functions

SYNOPSIS

      #include <openssl/bio.h>

      int    BIO_read(BIO *b, void *buf, int len);
      int    BIO_gets(BIO *b, char *buf, int size);
      int    BIO_write(BIO *b, const void *buf, int len);
      int    BIO_puts(BIO *b, const char *buf);

DESCRIPTION

     BIO_read() attempts to read len bytes from BIO b and places
     the data in buf.

     BIO_gets() performs the BIOs "gets" operation and places the
     data in buf. Usually this operation will attempt to read a
     line of data from the BIO of maximum length len. There are
     exceptions to this however, for example BIO_gets() on a
     digest BIO will calculate and return the digest and other
     BIOs may not support BIO_gets() at all.

     BIO_write() attempts to write len bytes from buf to BIO b.

     BIO_puts() attempts to write a null terminated string buf to
     BIO b.

RETURN VALUES

     All these functions return either the amount of data
     successfully read or written (if the return value is
     positive) or that no data was successfully read or written
     if the result is 0 or -1. If the return value is -2 then the
     operation is not implemented in the specific BIO type.

NOTES

     A 0 or -1 return is not necessarily an indication of an
     error. In particular when the source/sink is non-blocking or
     of a certain type it may merely be an indication that no
     data is currently available and that the application should
     retry the operation later.

     One technique sometimes used with blocking sockets is to use
     a system call (such as select(), poll() or equivalent) to
     determine when data is available and then call read() to
     read the data. The equivalent with BIOs (that is call
     select() on the underlying I/O structure and then call
     BIO_read() to read the data) should not be used because a
     single call to BIO_read() can cause several reads (and
     writes in the case of SSL BIOs) on the underlying I/O
     structure and may block as a result. Instead select() (or
     equivalent) should be combined with non blocking I/O so
     successive reads will request a retry instead of blocking.

1.0.2t               Last change: 2019-09-10                    1

BIO_read(3)                  OpenSSL                  BIO_read(3)

     See BIO_should_retry(3) for details of how to determine the
     cause of a retry and other I/O issues.

     If the BIO_gets() function is not supported by a BIO then it
     possible to work around this by adding a buffering BIO
     BIO_f_buffer(3) to the chain.

SEE ALSO

     BIO_should_retry(3)

     TBA

1.0.2t               Last change: 2019-09-10                    2

See also BIO_puts(3)
See also BIO_read(3)
See also BIO_write(3)