/usr/bin/env called from shebang hangs with an invocation that works from the command line.

hanging_env

root@server-12-ubuntu-1404:~# /usr/bin/env PATH=/opt/chef-server/embedded/bin ruby -e 'puts ENV["PATH"]'
/opt/chef-server/embedded/bin
root@server-12-ubuntu-1404:~# cat foo.rb
#!/usr/bin/env PATH=/opt/chef-server/embedded/bin ruby

puts ENV["PATH"]
root@server-12-ubuntu-1404:~# ./foo.rb
^C
root@server-12-ubuntu-1404:~#

strace(1) output: infinite loop of execve(2)

execve("./foo.rb", ["./foo.rb"], [/* 25 vars */]) = 0
brk(0)                                  = 0x1680000
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fabb8cab000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=20641, ...}) = 0
mmap(NULL, 20641, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fabb8ca5000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\37\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1845024, ...}) = 0
mmap(NULL, 3953344, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fabb86c5000
mprotect(0x7fabb8880000, 2097152, PROT_NONE) = 0
mmap(0x7fabb8a80000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1bb000) = 0x7fabb8a80000
mmap(0x7fabb8a86000, 17088, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fabb8a86000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fabb8ca4000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fabb8ca2000
arch_prctl(ARCH_SET_FS, 0x7fabb8ca2740) = 0
mprotect(0x7fabb8a80000, 16384, PROT_READ) = 0
mprotect(0x605000, 4096, PROT_READ)     = 0
mprotect(0x7fabb8cad000, 4096, PROT_READ) = 0
munmap(0x7fabb8ca5000, 20641)           = 0
brk(0)                                  = 0x1680000
brk(0x16a1000)                          = 0x16a1000
open("/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2919792, ...}) = 0
mmap(NULL, 2919792, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fabb83fc000
close(3)                                = 0
# ----------- repeats ----------- 
execve("./foo.rb", ["./foo.rb"], [/* 25 vars */]) = 0
brk(0)                                  = 0x1619000
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
[...]

Same effect if the shebang line is

#!/usr/bin/env PATH=/opt/chef-server/embedded/bin ruby -e 'puts ENV["PATH"]'

The shebang line limit is defined in/usr/include/linux/binfmts.h:

#define BINPRM_BUF_SIZE 128

And I'm only at 53.

An analogous shebang works fine on OS X 10.9.

Looks like computers are terrible: http://stackoverflow.com/a/10217307

tl;dr /usr/bin/env kinda doesn't really work right on Linux.