# About StringIO#ungetc

**URL:** <https://www.ruby-forum.com/t/about-stringio-ungetc/139389>\
**Category:** Development\
**Created:** [June 3, 2008, 2:10pm UTC](https://www.ruby-forum.com/t/about-stringio-ungetc/139389 "2008-06-03T14:10:19Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [June 3, 2008, 2:10pm UTC](https://www.ruby-forum.com/t/about-stringio-ungetc/139389/1 "2008-06-03T14:10:19Z")

</div>

e$B1sF#$G$9!#e(B

StringIO#ungetc e$B$G@hF,$r1[$($Fe(B ungetc  
e$B$7$h$&$H$7$?$H$-$N5sF0$,e(B  
e$B%I%-%e%a%s%H$H$"$C$F$$$^$;$s!#e(B

e$B5sF0e(B:  
$ ./ruby -v -rstringio -e ‘f = StringIO.new(“1234”); f.ungetc(?x); p  
f.getc’  
ruby 1.9.0 (2008-06-03 revision 16793) [i686-linux]  
“x”

e$B%I%-%e%a%s%He(B:

> Pushing back  
> behind the beginning of the buffer string is not possible. Nothing  
> will be done if such an attempt is made.

e$B$3$l$O\<BAu$N%P%0$G$7$g$&$+!#e(B

e$B$^$?!“e(Bungetc e$B$,85$NJ8;zNs$rJQ99$9$k$N$O;EMM$G$7$g$&$+!#e(B  
e$B$J$s$H$J$/!”!Ve(Breadonly e$B$J$i85$Ne(B string  
e$B$OJQ99$5$l$J$$!W$H$$$&e(B  
e$B;W$$$3$_$r$7$F$$$?$N$G5$$K$J$j$^$7$?!#;W$$$3$_$G$9$1$I!#e(B

e$B$D$$$G$K!"0J2\<$N5sF0$O%P%0$C$]$/8+$($^$9!#e(B

$ ./ruby -v -rstringio -e ’

> s = “\u3042\u3042\u3042”  
> f = StringIO.new(s, “r”)  
> f.getc  
> f.ungetc(?x)  
> p f.read  
> p s  
> ’  
> ruby 1.9.0 (2008-06-03 revision 16793) [i686-linux]  
> "\x81\x82xe$B$“e(B”  
> "e$B$"e(Bxe$B$“e(B”