1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
function eval -S -d "Evaluate parameters as a command"
# keep a copy of the previous $status and use restore_status
# to preserve the status in case the block that is evaluated
# does not modify the status itself.
set -l status_copy $status
function __fish_restore_status
return $argv[1]
end
if not set -q argv[2]
# like most builtins, we only check for -h/--help
# if we only have a single argument
switch "$argv[1]"
case -h --help
__fish_print_help eval
return 0
end
end
# If we are in an interactive shell, eval should enable full
# job control since it should behave like the real code was
# executed. If we don't do this, commands that expect to be
# used interactively, like less, wont work using eval.
set -l mode
if status --is-interactive-job-control
set mode interactive
else
if status --is-full-job-control
set mode full
else
set mode none
end
end
if status --is-interactive
status --job-control full
end
__fish_restore_status $status_copy
# To eval 'foo', we construct a block "begin ; foo; end <&3 3<&-"
# Note the redirections are also within the quotes.
#
# We then pipe this to 'source 3<&0’.
#
# You might expect that the dup2(3, stdin) should overwrite stdin,
# and therefore prevent 'source' from reading the piped-in block. This doesn't happen
# because when you pipe to a builtin, we don't overwrite stdin with the read end
# of the block; instead we set a separate fd in a variable 'builtin_stdin', which is
# what it reads from. So builtins are magic in that, in pipes, their stdin
# is not fd 0.
#
# ‘source’ does not apply the redirections to itself. Instead it saves them and passes
# them as block-level redirections to parser.eval(). Ultimately the eval’d code sees
# the following redirections (in the following order):
# dup2 0 -> 3
# dup2 pipe -> 0
# dup2 3 -> 0
# where the pipe is the pipe we get from piping ‘echo’ to ‘source’. Thus the redirection
# effectively makes stdin fd0, instead of the thing that was piped to ‘source’
echo "begin; $argv "\n" ;end <&3 3<&-" | source 3<&0
set -l res $status
status --job-control $mode
return $res
end
|
