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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 ...
String interpolation is an alternative to building string via concatenation, which requires repeat quoting and unquoting; [2] or substituting into a printf format string, where the variable is far from where it is used. Compare:
The number-to-string conversion of printf "%f" or sprintf "%f" round out even, use bankers' rounding. Perl also has a boolean context that it uses in evaluating conditional statements. The following values all evaluate as false in Perl:
In-place editing with perl -i is now safer; Initialisation of aggregate state variables; Full-size inode numbers; The sprintf %j format size modifier is now available with pre-C99 compilers; Close-on-exec flag set atomically; String- and number-specific bitwise ops are no longer experimental; Locales are now thread-safe on systems that support them
A common use case is in constructing printf or scanf format strings, where format specifiers are given by macros. [ 18 ] [ 19 ] A more complex example uses stringification of integers (by the preprocessor) to define a macro that expands to a sequence of string literals, which are then concatenated to a single string literal with the file name ...
The problem stems from the use of unchecked user input as the format string parameter in certain C functions that perform formatting, such as printf(). A malicious user may use the %s and %x format tokens, among others, to print data from the call stack or possibly other locations in memory.
In Perl % is the sigil for hashes. In many programming languages' string formatting operations (performed by functions such as printf and scanf), the percent sign denotes parts of the template string that will be replaced with arguments. (See printf format string.) In Python and Ruby the percent sign is also used as the string formatting operator.
Format is a function in Common Lisp that can produce formatted text using a format string similar to the print format string.It provides more functionality than print, allowing the user to output numbers in various formats (including, for instance: hex, binary, octal, roman numerals, and English), apply certain format specifiers only under certain conditions, iterate over data structures ...