[#BloombergLP-bdls-FdStreamBuf-underflow]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdls.adoc[bdls]::xref:BloombergLP/bdls/FdStreamBuf.adoc[FdStreamBuf]::underflow
:relfileprefix: ../../../
:mrdocs:

Replenish the input buffer and return the next character of input&period;

== Synopsis

Declared in `&lt;bdls&lowbar;fdstreambuf&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
virtual
int&lowbar;type
underflow() override;
----

== Description

Replenish the input buffer with data obtained from the file descriptor, and return the next character of input (or eof if no input is available)&period; Note that in windows text mode, &grave;&bsol;r &grave; sequences on the device will be translated to &grave; &grave;s&period;

== Return Value

the next character of input, or eof if none is available


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