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Currently (as of 2016) only a few regex engines (e.g., Perl's and Java's) can handle the full 21-bit Unicode range. Extending ASCII-oriented constructs to Unicode. For example, in ASCII-based implementations, character ranges of the form [x-y] are valid wherever x and y have code points in the range [0x00,0x7F] and codepoint(x) ≤ codepoint(y ...
It first appeared in AT&T System III UNIX in 1982. [4] The version of cut bundled in GNU coreutils was written by David M. Ihnat, David MacKenzie, and Jim Meyering. [5] The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities. [6]
rfind(string,substring) returns integer Description Returns the position of the start of the last occurrence of substring in string. If the substring is not found most of these routines return an invalid index value – -1 where indexes are 0-based, 0 where they are 1-based – or some value to be interpreted as Boolean FALSE. Related instr
The shells bash, zsh and PowerShell offer this as a specific feature. [69] [70] Shells which do not offer this as a specific feature may still be able to turn off echoing through some other means. Shells executing on a Unix/Linux operating system can use the stty external command to switch off/on echoing of input characters. [71]
string" is a substring of "substring" In formal language theory and computer science, a substring is a contiguous sequence of characters within a string. [citation needed] For instance, "the best of" is a substring of "It was the best of times". In contrast, "Itwastimes" is a subsequence of "It was the best of times", but not a substring.
A screenshot of the original 1971 Unix reference page for glob – the owner is dmr, short for Dennis Ritchie. glob() ( / ɡ l ɒ b / ) is a libc function for globbing , which is the archetypal use of pattern matching against the names in a filesystem directory such that a name pattern is expanded into a list of names matching that pattern.
Here, 0 is a single value pattern. Now, whenever f is given 0 as argument the pattern matches and the function returns 1. With any other argument, the matching and thus the function fail.
If the range of a function does not cover the entire space corresponding to the data type of the function's return value, a value known to be impossible under normal computation can be used. For example, consider the function index, which takes a string and a substring, and returns the integer index of the substring in the main string. If the ...