{"id":1798,"date":"2025-01-24T22:48:39","date_gmt":"2025-01-24T22:48:39","guid":{"rendered":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/?page_id=1798"},"modified":"2025-01-25T17:47:02","modified_gmt":"2025-01-25T17:47:02","slug":"stream-input","status":"publish","type":"page","link":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/topics\/c-details\/i-o-streams\/stream-input\/","title":{"rendered":"Stream Input"},"content":{"rendered":"\n

<\/span>Stream Input<\/span><\/h2>\n\n\n\n

<\/span>Stream-Extraction Operator<\/span><\/h3>\n\n\n\n

Stream input may be performed using the stream-extraction operator<\/em>:<\/p>\n\n\n\n

<\/span>The overloaded >> operator<\/span><\/h4>\n\n\n\n

The operator is overloaded to provide type-safe input of built-in types (int<\/strong>, char<\/strong>, long<\/strong>, short<\/strong>, unsigned<\/strong>, double<\/strong>, float<\/strong>, etc., plus string types and pointer values)<\/p>\n\n\n\n

For example:<\/p>\n\n\n\n

\n
\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  ostream<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 9\/2\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[]) <\/span><\/span>\n{<\/span><\/span>\n  <\/span>int<\/span> x, y;<\/span><\/span>\n<\/span>\n  <\/span>std<\/span>::cout << <\/span>"Enter two integers: "<\/span>;<\/span><\/span>\n  <\/span>std<\/span>::cin >> x >> y;<\/span><\/span>\n  <\/span>std<\/span>::cout << <\/span>"x = "<\/span> << x << <\/span>std<\/span>::endl<\/span><\/span>\n            << <\/span>"y = "<\/span> << y << <\/span>std<\/span>::endl;<\/span><\/span>\n<\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
\n
which outputs:<\/p>\n\n\n\n
Enter two integers: 56\n123<\/em>\nx = 56\ny = 123\nProgram ended with exit code: 0<\/code><\/pre>\n\n\n\n
\n
NOTE: The integers in italic, above, were input to the program.<\/p>\n<\/blockquote>\n<\/div>\n<\/div>\n\n\n\n
As with the <<<\/strong> operator, you can concatenate operators together.<\/p>\n\n\n\n
<\/span>Looping on Input until End of File<\/span><\/h4>\n\n\n\n
It is common to input a series of items from a stream, until the stream has no more items:<\/p>\n\n\n\n
\n
\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  ostream<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 9\/2\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[]) <\/span><\/span>\n{<\/span><\/span>\n  <\/span>char<\/span> <\/span>name<\/span>[<\/span>30<\/span>];<\/span><\/span>\n<\/span>\n  <\/span>std<\/span>::cout << <\/span>"Name[s]? (end-of-file ends): "<\/span>;<\/span><\/span>\n  <\/span>while<\/span> (<\/span>std<\/span>::cin >> name)<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Name = '"<\/span> << name << <\/span>'<\/span>\\'<\/span>'<\/span> << <\/span>std<\/span>::endl;<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Name? (end-of-file ends): "<\/span>;<\/span><\/span>\n  }<\/span><\/span>\n  <\/span>std<\/span>::cout << <\/span>"Goodbye!"<\/span> << <\/span>std<\/span>::endl;<\/span><\/span>\n<\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
\n
which outputs:<\/p>\n\n\n\n
Name[s]? (end-of-file ends): Bryan<\/em>\nName = 'Bryan'\nName? (end-of-file ends): Higgs<\/em>\nName = 'Higgs'\nName? (end-of-file ends): \u0004Goodbye!\nProgram ended with exit code: 0<\/code><\/pre>\n\n\n\n
\n
NOTE: The italicized text was input to the program. The last prompt received a Ctrl\/D, which caused an ‘end-of-file’.<\/p>\n<\/blockquote>\n<\/div>\n<\/div>\n\n\n\n
There are two code ‘idioms’ for testing for end-of-file:<\/p>\n\n\n\n
\n
\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  ostream<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 9\/2\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[]) <\/span><\/span>\n{<\/span><\/span>\n  <\/span>char<\/span> <\/span>name<\/span>[<\/span>30<\/span>];<\/span><\/span>\n<\/span>\n  <\/span>std<\/span>::cout << <\/span>"Name[s]? (end-of-file ends): "<\/span>;<\/span><\/span>\n  <\/span>while<\/span> (<\/span>std<\/span>::cin >> name)<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Name = '"<\/span> << name << <\/span>'<\/span>\\'<\/span>'<\/span> << <\/span>std<\/span>::endl;<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Name? (end-of-file ends): "<\/span>;<\/span><\/span>\n  }<\/span><\/span>\n  <\/span>std<\/span>::cout << <\/span>"Goodbye!"<\/span> << <\/span>std<\/span>::endl;<\/span><\/span>\n<\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  ostream<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 9\/2\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[]) <\/span><\/span>\n{<\/span><\/span>\n  <\/span>char<\/span> <\/span>name<\/span>[<\/span>30<\/span>];<\/span><\/span>\n<\/span>\n  <\/span>while<\/span> (<\/span>true<\/span>)<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Name[s]? (end-of-file ends): "<\/span>;<\/span><\/span>\n    <\/span>if<\/span> ( !(<\/span>std<\/span>::cin >> name) )<\/span><\/span>\n      <\/span>break<\/span>;<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Name = '"<\/span> << name << <\/span>'<\/span>\\'<\/span>'<\/span> << <\/span>std<\/span>::endl;<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>"Name = '"<\/span> << name << <\/span>'<\/span>\\'<\/span>'<\/span> << <\/span>std<\/span>::endl;<\/span><\/span>\n  }<\/span><\/span>\n  <\/span>std<\/span>::cout << <\/span>"Goodbye!"<\/span> << <\/span>std<\/span>::endl;<\/span><\/span>\n<\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n<\/div>\n\n\n\n
<\/span>get<\/strong> and getline<\/strong><\/span><\/h3>\n\n\n\n
<\/span>get()<\/span><\/h4>\n\n\n\n
The get<\/strong> member function with no arguments:<\/p>\n\n\n\n
int c = cin.get();<\/strong><\/code><\/pre>\n\n\n\n
inputs a single character from the specified stream.<\/p>\n\n\n\n
This version of get<\/strong> returns EOF<\/strong> when end of stream is found.<\/p>\n\n\n\n
The difference between >><\/strong> and get()<\/strong> is that the >><\/strong> operator normally ignores whitespace characters, while the get()<\/strong> function does not.<\/p>\n\n\n\n
Contrast:<\/p>\n\n\n\n
while (cin >> c)\n  cout << c;<\/strong><\/code><\/pre>\n\n\n\n
with:<\/p>\n\n\n\n
while ( (c = cin.get() ) != EOF)\n  cout.put(c);<\/strong><\/code><\/pre>\n\n\n\n
<\/span>get(char &)<\/span><\/h4>\n\n\n\n
The get(char &)<\/strong> member function inputs the next character from the input stream, and stores it in the character argument:<\/p>\n\n\n\n
char ch;\n\/\/ \u2026\ncin.get(ch);<\/strong><\/code><\/pre>\n\n\n\n
It returns:<\/p>\n\n\n\n