The command line has always used ad-hoc iteration protocols. How many times have you done something like
for x in *; do du -s $x; done
only to realize that you have a directory name with a space in it? Then you have to do something much more cumbersome, e.g.:
find -mindepth 1 -maxdepth 1 -print0 | xargs -0 du -s
Or have you ever tried to process a tab-delimited file, only to find that one of the columns can contain tab characters?
The problem is that item boundaries are signaled in-band, often without escaping. The solution is to use a generic syntax with proper escaping rules. Like JSON, for example. Or to use an out-of-band iteration protocol, like javascript iterators/generators. Javascript is also the natural way to process JSON. munj is a prototype for using javascript iterators/generators to do command-line data munging.
$ ./munj 'lines("test/delim.txt")'
[
"a b 1 c d x",
"a2 b2 2 c2 d2 x2",
" b3 3 c3 d3 x3"
]
$ ./munj 'sum(l.length for (l in lines("test/delim.txt")))'
41
$ ./munj 'ila("test/delim.txt")'
[
["a","b","1","c","d","x"],
["a2","b2","2","c2","d2","x2"],
["","b3","3","c3","d3","x3"]
]
$ ./munj '(l[1] for (l in ila("test/delim.txt")))'
[
"b",
"b2",
"b3"
]
$ ./munj 'lines("https://raw.github.com/skinner/munj/master/test/delim.txt")'
[
"a b 1 c d x",
"a2 b2 2 c2 d2 x2",
" b3 3 c3 d3 x3"
]
$ ./munj '(l for (l in lines("test/delim.txt")) if (l.match(/b\d/)))'
[
"a2 b2 2 c2 d2 x2",
" b3 3 c3 d3 x3"
]
$ ./munj 'interleave(lines("test/delim.txt"), lines("test/delim.txt"))'
[
"a b 1 c d x",
"a b 1 c d x",
"a2 b2 2 c2 d2 x2",
"a2 b2 2 c2 d2 x2",
" b3 3 c3 d3 x3",
" b3 3 c3 d3 x3"
]
$ ./munj 'range(1, 6)'
[
1,
2,
3,
4,
5
]
$ ./munj 'zip(range(0, 2), range(5, 8), range(10, 14))'
[
[0,5,10],
[1,6,11],
[null,7,12],
[null,null,13]
]
$ ./munj 'concat(range(1, 3), range(6, 8))'
[
1,
2,
6,
7
]
$ ./munj "sample(5, range(0, 100000))"
[
98677,
6027,
91333,
25585,
35203
]
$ ./munj 'filter(function(x){return 0 == x % 2;}, range(1, 10))'
[
2,
4,
6,
8
]
$ ./munj 'ls()'
[
"test",
"munj.js",
".git",
"munj",
".gitignore",
"README"
]
$ ./munj 'take(3, range(1, 6))'
[
1,
2,
3
]
$ ./munj 'drop(2, range(1, 6))'
[
3,
4,
5
]
$ ./munj 'tail(2, range(1, 6))'
[
4,
5
]
$ ./munj 'sum(range(1, 6))'
15
$ ./munj 'product(range(1, 6))'
120
$ ./munj 'reduce(function(x, y) {return x + "-" + y}, "", range(1, 6))'
"-1-2-3-4-5"
$ ./munj 'values([4, 8, 15, 16, 23, 42])'
[
4,
8,
15,
16,
23,
42
]
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