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In computer science, an illegal character is a character that is not allowed by a certain programming language, protocol, or program. [1] To avoid illegal characters, some languages may use an escape character which is a backslash followed by another character.
In computing, echo is a command that outputs the strings that are passed to it as arguments. It is a command available in various operating system shells and typically used in shell scripts and batch files to output status text to the screen [ 1 ] or a computer file , or as a source part of a pipeline .
For example, in Python, raw strings are preceded by an r or R – compare 'C:\\Windows' with r'C:\Windows' (though, a Python raw string cannot end in an odd number of backslashes). Python 2 also distinguishes two types of strings: 8-bit ASCII ("bytes") strings (the default), explicitly indicated with a b or B prefix, and Unicode strings ...
If the above is stored in the executable file ./check, the shell command ./check " 1 ) evil" will attempt to execute the injected shell command evil instead of comparing the argument with the constant one. Here, the code under attack is the code that is trying to check the parameter, the very code that might have been trying to validate the ...
In UTF-16, a BOM (U+FEFF) may be placed as the first bytes of a file or character stream to indicate the endianness (byte order) of all the 16-bit code units of the file or stream. If an attempt is made to read this stream with the wrong endianness, the bytes will be swapped, thus delivering the character U+FFFE , which is defined by Unicode as ...
special characters that are not available in the limited character set are stored in the form of a multi-character code; there are usually two or three equivalent representations, e.g. for the character € the named character reference € and the decimal character reference € and the hexadecimal character reference €. The edit ...
Python supports a wide variety of string operations. Strings in Python are immutable, so a string operation such as a substitution of characters, that in other programming languages might alter the string in place, returns a new string in Python. Performance considerations sometimes push for using special techniques in programs that modify ...
Generally, an escape character is not a particular case of (device) control characters, nor vice versa.If we define control characters as non-graphic, or as having a special meaning for an output device (e.g. printer or text terminal) then any escape character for this device is a control one.