Output can be interleaved without sync_with_stdio(),
since the C++ standard
streams are based on z/OS® XL C I/O.
That is, cout can be interleaved with stdout,
and clog can be interleaved with stderr.
This is done by explicitly flushing cout or clog before
calling the z/OS XL C output
function. Results of attempting to interleave these streams without
explicitly flushing, are undefined. Output to cerr doesn't
have to be explicitly flushed, since cerr is unit-buffered.
Input to cin may be interleaved with input to stdin,
without sync_with_stdio(), on a line-by-line basis.
Results of attempting to interleave on a per-character basis are undefined. Figure 1 shows an example program and the
output it produces.
Figure 1. Interleaving I/O without
sync_with_stdio()// Example of interleaving I/O without sync_with_stdio()
//
// tsyncwos.cxx
#include <stdio.h>
#include <fstream.h>
int main() {
cout << "object: to illustrate interleaving input and output\n "
" without sync_with_stdio()\n" << endl;
printf( "interleaving output ");
cout << "works with an (end of line 1) \n" << flush;
cout << "explicit flush of cout " << flush;
printf( "(end of line 2)\n\n");
char string1[80] = "";
char string2[80] = "";
char string3[80] = "";
char* rc = NULL;
cout << "type the following 3 lines:\n"
"interleaving input\n"
"on a per-line basis\n"
"is supported\n" << endl;
cin.getline(string1, 80);
rc = gets(string2);
cin.getline(string3, 80);
cout << "\nstring1 is \"" << string1 << "\"\n"
<< "string2 is \"" << string2 << "\"\n"
<< "string3 is \"" << string3 << "\"\n" << endl;
// The endl manipulator inserts a newline
// character and calls flush().
char char1 = '\0';
char char2 = '\0';
char char3 = '\0';
cout << "type the following 2 lines:\n"
"results of interleaving input on a per-\n"
"character basis are not defined\n" << endl;
cin >> char1;
char2 = (char) getchar();
cin >> char3;
cout << "\nchar1 is \'" << char1 << "\'\n"
<< "char2 is \'" << char2 << "\'\n"
<< "char3 is \'" << char3 << "\'\n" << flush;
}
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// sample output (with user input shown underlined):
//
// object: to illustrate interleaving input and output
// without sync_with_stdio()
//
// interleaving output works with an (end of line 1)
// explicit flush of cout (end of line 2)
//
// type the following 3 lines:
// interleaving input
// on a per-line basis
// is supported
//
// interleaving-input
// on a per-line basis
// is supported
//
// string1 is "interleaving input"
// string2 is "on a per-line basis"
// string3 is "is supported"
//
// type the following 2 lines:
// results of interleaving input on a per-
// character basis are not defined
//
// results of interleaving input on a per-
// character basis are not defined
//
// char1 is 'r'
// char2 is 'c'
// char3 is 'e'
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