[#bsl-basic_string-0faf-substr-0d9]
= xref:bsl.adoc[bsl]::xref:bsl/basic_string-0faf.adoc[basic_string]::substr
:relfileprefix: ../../
:mrdocs:

Return a substring of this string as a const lvalue.

== Synopsis

Declared in `<bslstl_string.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:bsl/basic_string-0faf.adoc[basic_string]
substr(
    xref:bsl/basic_string-0faf/size_type.adoc[size_type] position = 0,
    xref:bsl/basic_string-0faf/size_type.adoc[size_type] numChars = npos) const &;
----

== Description

Return a string whose value is the substring starting at the optionally specified `position` in this string, of length the optionally specified `numChars` or `length() ‐ position`, whichever is smaller. If `position` is not specified, 0 is used (i.e., the substring is from the beginning of this string). If `numChars` is not specified, `npos` is used (i.e., the entire suffix from `position` to the end of the string is returned).

== Return Value

substring of this string

== Parameters

[cols="1,4"]
|===
| Name| Description
| *position*
| starting index
| *numChars*
| number of characters
|===


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