This is a collection of one-line quines in several languages. A quine is a program that outputs its own source code, and in theory such a program exists for any Turing-complete programming language with an output feature (essentially all programming languages in common use today).
Although the quines are only one line, they are not attempts to find the shortest quines possible. Many "redundant" parts are kept to maintain some readability and good style. The quines are also meant to be portable across a wide variety of implementations, although some alternatives are provided that make certain assumptions.
All original code is dedicated to the public domain under Creative Commons CC0 1.0 Universal (a copy is available in LICENSE.txt). The Rust code is available under Creative Commons Attribution-ShareAlike 3.0 Unported (a copy is available in LICENSE-Rust.txt), as it is derived from code that uses that license.
Note: Some files have a newline at the end while others do not. This is intentional because the output functions available in different languages either add a newline or omit it. In most cases it is easy to adjust the program to either add or remove a newline at the end of the file.
Programs are available for Linux on x86 (32-bit) and x86-64 architectures, and are written for the GNU Assembler. They do not depend on the C standard library and should be statically linked. By their very nature, these programs are not portable across platforms.
The entry point is named s rather than the conventional _start. As a result, the symbol must be explicitly specified to the linker. For GNU ld, this is given by the -e option.
GNU Assembler requires a newline at the end of the source code, although it only gives a warning and still assembles the code without it. The code can be shortened if the newline is omitted.
The program is compatible with POSIX.1-2004. The input is not used.
The main program is compatible with C89 and makes very few assumptions. The code can be shortened a bit by assuming that the character encoding is ASCII (olq_ascii.c) and also by assuming support for POSIX-style positional format specifiers (olq_posix.c). (Of course, these two assumptions may be combined.)
The declaration for printf at the beginning is needed because other code cannot be on the same line as an #include, which poses a problem for a one-line program.
The main program is compatible with C# 1.0 and essentially all implementations of the BCL. The code can be shortened substantially by using top-level statements, introduced in C# 9 (olq_cs9.cs).
The program is compatible with Emojicode 0.7.0 and later (latest version tested is Emojicode 1.0 beta 2).
The program is compatible with F# 2.0.
The program is compatible with ANS Forth.
The program is compatible with Go 1.
The program is compatible with Haskell 98.
The program is compatible with Java SE 5 (when the PrintStream.printf and related string formatting methods were added).
The main program is compatible with ECMAScript 5 (when the JSON functions were added). The code can be shortened by using some ECMAScript 6 features (olq_es6.js), namely template literals and arrow functions.
The program is compatible with Lua 5.0.
The main program is compatible with Perl 5.8.0 (when the POSIX-style positional format specifiers were introduced for printf). Like in C, the main program does not assume a particular character encoding, although it does use POSIX-style positional format specifiers as mentioned previously. The code can be shortened a bit by assuming that the character encoding is ASCII (olq_ascii.pl).
The program is compatible with PHP 4.
The main program uses the str.format method introduced in Python 3, even though the code that uses the older printf-style string formatting (olq_percent.py) is shorter.
The program is compatible with Ruby 2.0.
This posed a challenge because the format string to print! and related macros must be a string literal, which means that a format string cannot be its own argument as in other languages. The solution is admittedly not original, as it is adapted from a submission to Programming-Idioms.org, originally added by r0t0m0l0t0v.
The program is compatible with R5RS.
The program is compatible with the POSIX shell language as defined in POSIX.1-2004.