Is there a C++ version of ungetc?

Question

That is, can I put a character back onto an istream?

score 6 · Accepted Answer · edited May 23 '17 at 09:58

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Yes. istream::putback is the same as ungetc except if using unget():

You can't lie with unget(). It "ungets" the last-read character. You can lie with putback(c). You can "putback" some character other than the last-read character. Sometimes putting back a character other than the last-read character can be useful.

Also, if the underlying read buffer really does have buffering capability, you can "putback" more than one character. I think ungetc() is limited to one character.

edited May 23 '17 at 09:58

Community

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answered Aug 02 '11 at 16:09

`istream::unget` is not `ungetc`. You can lie with `ungetc`. – R. Martinho Fernandes Aug 02 '11 at 16:12
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@Martinho: That's just `putback` instead – Puppy Aug 02 '11 at 16:17
Probably also worth mentioning the `peek` method, because most wants for `unget` are just the second step of implementing "I want to peek the next character". – mtraceur Jun 11 '23 at 01:02

score 2 · Answer 2 · answered Aug 02 '11 at 16:07

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You can put a character back with the istream::putback function. You can even put a different character if you want.

answered Aug 02 '11 at 16:07

R. Martinho Fernandes

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score 0 · Answer 3 · answered Aug 02 '11 at 16:07

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Yes, http://www.cplusplus.com/reference/iostream/istream/putback/

answered Aug 02 '11 at 16:07

Prof. Falken

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Is there a C++ version of ungetc?

3 Answers3