A lightweight shell scripting language
Blueshell (a working title) focuses on allowing the programmer to write better Bash scripts. Any Bash script can and should be instead written in Blueshell.
But why?
Blueshell offers predictable syntax and useful high-level constructs, while still providing a direct and simple interface to execute Bash commands.
Some useful constructs allow direct and simple access to the shell:
$> touch foo.txt Runs a command, exiting the script if the command fails. Stdout, stderr, and stdin are connected directly to the terminal.
out = $> ls Runs a command and captures its output, exiting the script if the command fails. Stderr and stdin are ignored.
out, err = try $> python might_fail.py Try to run a command and capture its output. If the command exits non-zero, then the error code is also returned and the script does not exit.
try $> python might_fail.py Similar to the above, except leaves stdout, stderr, and stdin connected to the terminal, and ignores the error code. Semantically, the standalone try is the same as any command in a Bash script.
$> echo "${'Hello, ' + 'world!'}" > ${file}.txt Expressions can be injected into commands with ${E}.
cd '~/dir' { ... } Execute a block of code within a given directory.
Example:
ok := true
cd '~/dev/blueshell' {
$> ocamlbuild -use-ocamlfind src/main.byte
tests := $> ls test/integration/progs/basic/*.blu
for t in tests.split('\n') {
exp_out := $> cat ${t}.out
out, err := try $> ./main.byte ${t}
if err != 0 || out != exp_out {
print t + ' failed'
ok = false
}
}
}
if ok {
print 'All tests passed!'
}
The above Blueshell script compiles the Blueshell interpreter and runs all of our basic integration tests, making sure all of the tests exit cleanly and produce expected output!
- Error objects
- Change
printtoprintln, and then makeprintnot output newlines. - HTTP support
argv List of command line arguments, with the running file at index 0.
max(n1, n2) Returns max of n1 and n2, which can be either floats or ints.
typeof(x) Returns type string of variable x.
open(filepath) TODO Returns open file object for file at filepath.
s[i] Returns character at i in s.
s[i] = c Sets character at i to c in s. The length of c must be 1.
s[start:stop] Returns a slice of s from index start (inclusive) to index stop (exclusive). If start or stop is omitted, then 0 and s.len() is used, respectively. The stop index is normalized, meaning -1 evals to s.len()-1, -2 evals to s.len()-2, etc.
s.len() Returns length of s.
s.split(pattern) Splits s according to regex string pattern and returns list of substrings.
s.replace(pattern, s2) Replaces substrings in s matched by regex string pattern with string s2.
s.fmt(...) Returns new string with embedded formats of "{}" in s replaced by corresponding argument by position (fmt accepts variable number of arguments). Values will be automatically converted to strings. Example: "Hello, {}! The number is {}.".fmt('Cody', 42) returns "Hello, Cody! The number is 42.".
l[i] Returns element at i in l.
l[i] = x Sets element at i to x in l.
l[start:stop] Returns a slice of l. See str slice for details.
l.len() Returns length of l.
l.push(x) Pushes x to end of l.
l.pushf(x) TODO Pushes x to front of l.
l.pop() Removes and returns last element of l.
l.popf() TODO Removes and returns first element of l.
l.extend(l2) TODO Adds all elements of list l2 to end of l.
l.map(f) TODO Applies function f to every element of l, returning a new list with the results.
l.filter(f) TODO Filters l by function f, returning a new list with elements that f returns true on.
l.sort(f) TODO Sorts l using comparator function f.
d[k] Returns corresponding value of key k in d.
d[k] = v Sets key k to value v in d.
d.len() Returns length of d.
d.del(k) Deletes key k from d.
f.read() TODO Returns string contents of f.
f.lines() TODO Returns iterator over the lines of f.
f.write(s) TODO Overwrites contents of f with string s.
f.append(s) TODO Appends string s to the end of f.