ruby, 47 bytes

Result

WA

Duration

1176ms

Code [DL]

puts $<.chars.map{|c|c>'@'&&c<'['?'1':'0'}.join

stdin

abCDEFgHIJkLmNOpQrSTuVWxyz

stdout

001111011101011010110110000

stderr

/volume/CODE:1: warning: ARGF#chars is deprecated; use #each_char instead

strace

11    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffe6efbddf0 /* 9 vars */) = 0
13    execve("/usr/local/ruby-2.7.1/bin/ruby", ["/usr/local/ruby-2.7.1/bin/ruby", "/volume/CODE"], 0x558e7419ed60 /* 9 vars */ <unfinished ...>
12    execve("/bin/cat", ["cat", "-"], 0x558e7419ed40 /* 9 vars */) = 0
13    <... execve resumed>)             = 0
12    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
13    +++ exited with 0 +++
11    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=0, si_utime=7, si_stime=5} ---
11    +++ exited with 0 +++