sed, 41 bytes

Result

AC

Duration

690ms

Code [DL]

1h
${:1
x
s/ $//
t1
x
:2
s/K /KK/
t2
h}
g

stdin

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K                                                 

stdout

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KKKKKKKKKKK

stderr

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffeb21950d0 /* 7 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x55d3c4247cf8 /* 7 vars */) = 0
11    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
13    execve("/usr/bin/sed", ["/usr/bin/sed", "-f", "/volume/CODE"], 0x55d3c43bedb0 /* 7 vars */ <unfinished ...>
12    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
13    <... execve resumed> )            = 0
13    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
10    +++ exited with 0 +++