added readme

README.md

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+# echo-rs
+
+My rewrite of the echo GNU core utility in rust
+
+version: 0.1.0
+author: [Lu Baumann](https://blog.surferlul.me/)
+
+## usage
+
+refer to `echo-rs --help`:
+
+```
+Usage: echo-rs [SHORT-OPTION]... [STRING]...
+  or:  echo-rs LONG-OPTION
+Echo the STRING(s) to standard output. Rust rewrite of GNU echo util.
+
+  -n             do not output the trailing newline
+  -e             enable interpretation of backslash escapes
+  -E             disable interpretation of backslash escapes (default)
+      --help     display this help and exit
+      --version  output version information and exit
+
+If -e is in effect, the following sequences are recognized:
+
+  \\      backslash
+  \a      alert (BEL)
+  \b      backspace
+  \c      produce no further output
+  \e      escape
+  \f      form feed
+  \n      new line
+  \r      carriage return
+  \t      horizontal tab
+  \v      vertical tab
+  \0NNN   byte with octal value NNN (1 to 3 digits)
+  \xHH    byte with hexadecimal value HH (1 to 2 digits)
+```
+
+## testing
+
+test script requires python >= 3.10
+
+`gnu_echo_tests/test.py -e /bin/echo -b <path/to/echo-rs>`
+
+| parameter        | value                                   |
+| ---------------- | --------------------------------------- |
+| `-e`, `--echo`   | path to echo executable to test against |
+| `-b`, `--binary` | path to echo-rs binary to test          |