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The formatting placeholders in scanf are more or less the same as that in printf, its reverse function.As in printf, the POSIX extension n$ is defined. [2]There are rarely constants (i.e., characters that are not formatting placeholders) in a format string, mainly because a program is usually not designed to read known data, although scanf does accept these if explicitly specified.
The format string syntax and semantics is the same for all of the functions in the printf-like family. Mismatch between the format specifiers and count and type of values can cause a crash or vulnerability. The printf format string is complementary to the scanf format string, which provides formatted input (lexing a.k.a. parsing). Both format ...
Most of these are only useful for detecting bad format strings that are known at compile-time. If the format string may come from the user or from a source external to the application, the application must validate the format string before using it. Care must also be taken if the application generates or selects format strings on the fly.
Both take one argument that specifies the formatting of the output, and any number of arguments that provide the values to be formatted. Variadic functions can expose type-safety problems in some languages. For instance, C's printf, if used incautiously, can give rise to a class of security holes known as format string attacks.
For function that manipulate strings, modern object-oriented languages, like C# and Java have immutable strings and return a copy (in newly allocated dynamic memory), while others, like C manipulate the original string unless the programmer copies data to a new string.
Several compilers support variable-argument macros when compiling C and C++ code: the GNU Compiler Collection 3.0, [4] Clang (all versions), [8] Visual Studio 2005, [6] C++Builder 2006, and Oracle Solaris Studio (formerly Sun Studio) Forte Developer 6 update 2 (C++ version 5.3). [9] GCC also supports such macros when compiling Objective-C.
In Visual Basic (and Visual Basic for Applications) the Variant data type is a tagged union that can be used to represent any other data type (for example, integer, floating-point, single- and double-precision, object, etc.) except fixed-length string type. In Visual Basic, any variable not declared explicitly or the type of which is not ...
As an example, VBA code written in Microsoft Access can establish references to the Excel, Word and Outlook libraries; this allows creating an application that – for instance – runs a query in Access, exports the results to Excel and analyzes them, and then formats the output as tables in a Word document or sends them as an Outlook email.