Why does Perl's print fail to output anything to STDOUT and STDERR, but writes to a file successfully?

Question

I'm attempting to print to standard out from the following Perl script, but it doesn't produce any output on the screen. It does print to a file, however.

#!/usr/bin/perl
use warnings;
use strict;

print "Here's some text\n";
print STDERR "Here's some text\n";
print STDOUT "Here's some text\n";

open FH, ">", "file.txt" or die $!;

print FH "Here's some text\n";

I tried checking the version of perl I'm using (perl -v), but that doesn't output anything either. The perl man page tells me I'm using 5.14.2. I'm running the Perl script from a bash prompt from a Raspberry Pi.

I saw this similar post Print: producing no output, so I used strace and saw that the output did not include any write commands.

strace perl -we'print("a") or die("Can'\''t print: $!\n");'

Here's the strace output for the full script:

execve("./response", ["./response"], [/* 18 vars */]) = 0
brk(0)                                  = 0xd98000
uname({sys="Linux", node="raspberrypi", ...}) = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f99000
access("/etc/ld.so.preload", R_OK)      = 0
open("/etc/ld.so.preload", O_RDONLY)    = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=44, ...}) = 0
mmap2(NULL, 44, PROT_READ|PROT_WRITE, MAP_PRIVATE, 3, 0) = 0xb6f98000
close(3)                                = 0
open("/usr/lib/arm-linux-gnueabihf/libcofi_rpi.so", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\270\4\0\0004\0\0\0"..., 512) = 512
lseek(3, 7276, SEEK_SET)                = 7276
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
lseek(3, 7001, SEEK_SET)                = 7001
read(3, "A.\0\0\0aeabi\0\1$\0\0\0\0056\0\6\6\10\1\t\1\n\2\22\4\24\1\25"..., 47) = 47
fstat64(3, {st_mode=S_IFREG|0755, st_size=10170, ...}) = 0
mmap2(NULL, 39740, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6f6c000
mprotect(0xb6f6e000, 28672, PROT_NONE)  = 0
mmap2(0xb6f75000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1) = 0xb6f75000
close(3)                                = 0
munmap(0xb6f98000, 44)                  = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=64456, ...}) = 0
mmap2(NULL, 64456, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb6f5c000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/usr/lib/libperl.so.5.14", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\220\v\2\0004\0\0\0"..., 512) = 512
lseek(3, 1346508, SEEK_SET)             = 1346508
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1120) = 1120
lseek(3, 1346184, SEEK_SET)             = 1346184
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0056\0\6\6\10\1\t\1\n\2\22\4\24\1\25"..., 51) = 51
fstat64(3, {st_mode=S_IFREG|0644, st_size=1347628, ...}) = 0
mmap2(NULL, 1379192, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6e0b000
mprotect(0xb6f4f000, 32768, PROT_NONE)  = 0
mmap2(0xb6f57000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x144) = 0xb6f57000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/arm-linux-gnueabihf/libdl.so.2", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0(\t\0\0004\0\0\0"..., 512) = 512
lseek(3, 8652, SEEK_SET)                = 8652
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1160) = 1160
lseek(3, 8320, SEEK_SET)                = 8320
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0056\0\6\6\10\1\t\1\n\2\22\4\24\1\25"..., 49) = 49
fstat64(3, {st_mode=S_IFREG|0644, st_size=9812, ...}) = 0
mmap2(NULL, 41136, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6e00000
mprotect(0xb6e02000, 28672, PROT_NONE)  = 0
mmap2(0xb6e09000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1) = 0xb6e09000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/arm-linux-gnueabihf/libm.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\3201\0\0004\0\0\0"..., 512) = 512
lseek(3, 426468, SEEK_SET)              = 426468
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1160) = 1160
lseek(3, 426136, SEEK_SET)              = 426136
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0056\0\6\6\10\1\t\1\n\2\22\4\24\1\25"..., 49) = 49
fstat64(3, {st_mode=S_IFREG|0644, st_size=427628, ...}) = 0
mmap2(NULL, 458912, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6d8f000
mprotect(0xb6df7000, 28672, PROT_NONE)  = 0
mmap2(0xb6dfe000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x67) = 0xb6dfe000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/arm-linux-gnueabihf/libpthread.so.0", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\274V\0\0004\0\0\0"..., 512) = 512
lseek(3, 82712, SEEK_SET)               = 82712
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1400) = 1400
lseek(3, 82308, SEEK_SET)               = 82308
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0056\0\6\6\10\1\t\1\n\2\22\4\24\1\25"..., 49) = 49
fstat64(3, {st_mode=S_IFREG|0755, st_size=116462, ...}) = 0
mmap2(NULL, 123412, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6d70000
mprotect(0xb6d84000, 28672, PROT_NONE)  = 0
mmap2(0xb6d8b000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x13) = 0xb6d8b000
mmap2(0xb6d8d000, 4628, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb6d8d000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/arm-linux-gnueabihf/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\214y\1\0004\0\0\0"..., 512) = 512
lseek(3, 1215264, SEEK_SET)             = 1215264
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1360) = 1360
lseek(3, 1214828, SEEK_SET)             = 1214828
read(3, "A.\0\0\0aeabi\0\1$\0\0\0\0056\0\6\6\10\1\t\1\n\2\22\4\24\1\25"..., 47) = 47
fstat64(3, {st_mode=S_IFREG|0755, st_size=1216624, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f98000
mmap2(NULL, 1258784, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6c3c000
mprotect(0xb6d62000, 32768, PROT_NONE)  = 0
mmap2(0xb6d6a000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x126) = 0xb6d6a000
mmap2(0xb6d6d000, 9504, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb6d6d000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/arm-linux-gnueabihf/libcrypt.so.1", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\30\7\0\0004\0\0\0"..., 512) = 512
lseek(3, 29116, SEEK_SET)               = 29116
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1160) = 1160
lseek(3, 28780, SEEK_SET)               = 28780
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0056\0\6\6\10\1\t\1\n\2\22\4\24\1\25"..., 49) = 49
fstat64(3, {st_mode=S_IFREG|0644, st_size=30276, ...}) = 0
mmap2(NULL, 221504, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6c05000
mprotect(0xb6c0c000, 28672, PROT_NONE)  = 0
mmap2(0xb6c13000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6) = 0xb6c13000
mmap2(0xb6c15000, 155968, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb6c15000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/arm-linux-gnueabihf/libgcc_s.so.1", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0`\364\0\0004\0\0\0"..., 512) = 512
lseek(3, 130212, SEEK_SET)              = 130212
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1160) = 1160
lseek(3, 129880, SEEK_SET)              = 129880
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0056\0\6\6\10\1\t\1\n\2\22\4\24\1\25"..., 51) = 51
fstat64(3, {st_mode=S_IFREG|0644, st_size=131372, ...}) = 0
mmap2(NULL, 162704, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6bdd000
mprotect(0xb6bfd000, 28672, PROT_NONE)  = 0
mmap2(0xb6c04000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1f) = 0xb6c04000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f97000
set_tls(0xb6f976d0, 0xb6f97da8, 0xb6f9c048, 0xb6f976d0, 0xb6f9c048) = 0
mprotect(0xb6c13000, 4096, PROT_READ)   = 0
mprotect(0xb6d6a000, 8192, PROT_READ)   = 0
mprotect(0xb6d8b000, 4096, PROT_READ)   = 0
mprotect(0xb6dfe000, 4096, PROT_READ)   = 0
mprotect(0xb6e09000, 4096, PROT_READ)   = 0
mprotect(0xb6f57000, 8192, PROT_READ)   = 0
mprotect(0x11000, 4096, PROT_READ)      = 0
mprotect(0xb6f9b000, 4096, PROT_READ)   = 0
munmap(0xb6f5c000, 64456)               = 0
set_tid_address(0xb6f97278)             = 12607
set_robust_list(0xb6f97280, 0xc)        = 0
futex(0xbece6778, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 1, NULL, b6d8c000) = -1 EAGAIN (Resource temporarily unavailable)
rt_sigaction(SIGRTMIN, {0xb6d7520c, [], SA_SIGINFO|0x4000000}, NULL, 8) = 0
rt_sigaction(SIGRT_1, {0xb6d750b4, [], SA_RESTART|SA_SIGINFO|0x4000000}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
getrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM_INFINITY}) = 0
rt_sigaction(SIGFPE, {SIG_IGN, [FPE], SA_RESTART|0x4000000}, {SIG_DFL, [], 0}, 8) = 0
brk(0)                                  = 0xd98000
brk(0xdb9000)                           = 0xdb9000
getuid32()                              = 1001
geteuid32()                             = 1001
getgid32()                              = 1004
getegid32()                             = 1004
open("/usr/lib/locale/locale-archive", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=1534656, ...}) = 0
mmap2(NULL, 1534656, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb6a66000
close(3)                                = 0
open("/dev/urandom", O_RDONLY|O_LARGEFILE) = 3
read(3, "~\210\223\234", 4)             = 4
close(3)                                = 0
gettimeofday({1460938704, 307768}, NULL) = 0
readlink("/proc/self/exe", "/usr/bin/perl", 4095) = 13
stat64("/usr/local/lib/site_perl/5.14.2/arm-linux-gnueabihf-thread-multi-64int", 0xbece6368) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/site_perl/5.14.2", 0xbece6368) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/site_perl/arm-linux-gnueabihf-thread-multi-64int", 0xbece6368) = -1 ENOENT (No such file or directory)
open("./response", O_RDONLY|O_LARGEFILE) = 3
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbece627c) = -1 ENOTTY (Inappropriate ioctl for device)
_llseek(3, 0, [0], SEEK_CUR)            = 0
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
brk(0xddb000)                           = 0xddb000
read(3, "#!/usr/bin/perl\nuse warnings;\nus"..., 8192) = 210
stat64("/etc/perl/warnings.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/etc/perl/warnings.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/perl/5.14.2/warnings.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/perl/5.14.2/warnings.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/local/share/perl/5.14.2/warnings.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/local/share/perl/5.14.2/warnings.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/warnings.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/warnings.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/share/perl5/warnings.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/share/perl5/warnings.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl/5.14/warnings.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl/5.14/warnings.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/share/perl/5.14/warnings.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/share/perl/5.14/warnings.pm", {st_mode=S_IFREG|0644, st_size=15015, ...}) = 0
open("/usr/share/perl/5.14/warnings.pm", O_RDONLY|O_LARGEFILE) = 4
ioctl(4, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbece5be4) = -1 ENOTTY (Inappropriate ioctl for device)
_llseek(4, 0, [0], SEEK_CUR)            = 0
read(4, "# -*- buffer-read-only: t -*-\n# "..., 8192) = 8192
read(4, "08\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x"..., 8192) = 6823
read(4, "", 8192)                       = 0
close(4)                                = 0
brk(0xdfc000)                           = 0xdfc000
stat64("/etc/perl/strict.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/etc/perl/strict.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/perl/5.14.2/strict.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/local/lib/perl/5.14.2/strict.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/local/share/perl/5.14.2/strict.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/local/share/perl/5.14.2/strict.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/strict.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/strict.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/share/perl5/strict.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/share/perl5/strict.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl/5.14/strict.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl/5.14/strict.pm", 0xbece5d90) = -1 ENOENT (No such file or directory)
stat64("/usr/share/perl/5.14/strict.pmc", 0xbece5e10) = -1 ENOENT (No such file or directory)
stat64("/usr/share/perl/5.14/strict.pm", {st_mode=S_IFREG|0644, st_size=879, ...}) = 0
open("/usr/share/perl/5.14/strict.pm", O_RDONLY|O_LARGEFILE) = 4
ioctl(4, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbece5be4) = -1 ENOTTY (Inappropriate ioctl for device)
_llseek(4, 0, [0], SEEK_CUR)            = 0
read(4, "package strict;\n\n$strict::VERSIO"..., 8192) = 879
_llseek(4, 878, [878], SEEK_SET)        = 0
_llseek(4, 0, [878], SEEK_CUR)          = 0
close(4)                                = 0
read(3, "", 8192)                       = 0
open("file.txt", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 4
ioctl(4, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbece614c) = -1 ENOTTY (Inappropriate ioctl for device)
_llseek(4, 0, [0], SEEK_CUR)            = 0
fstat64(4, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0
rt_sigaction(SIG_0, NULL, {0xb6e18dc4, [TRAP RTMIN RT_1 RT_2 RT_3 RT_12 RT_13 RT_15 RT_16 RT_18 RT_19 RT_20 RT_25 RT_26 RT_27 RT_28 RT_29], SA_SIGINFO|0x85b8}, 8) = -1 EINVAL (Invalid argument)
rt_sigaction(SIGHUP, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGINT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGQUIT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGILL, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGTRAP, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGABRT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGBUS, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGFPE, NULL, {SIG_IGN, [FPE], SA_RESTART|0x4000000}, 8) = 0
rt_sigaction(SIGKILL, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGUSR1, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSEGV, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGUSR2, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGPIPE, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGALRM, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSTKFLT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCONT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSTOP, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGTSTP, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGTTIN, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGTTOU, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGURG, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGXCPU, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGXFSZ, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGVTALRM, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGPROF, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGWINCH, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGIO, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGPWR, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSYS, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_2, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_3, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_4, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_5, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_6, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_7, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_8, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_9, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_10, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_11, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_12, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_13, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_14, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_15, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_16, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_17, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_18, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_19, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_20, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_21, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_22, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_23, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_24, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_25, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_26, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_27, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_28, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_29, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_30, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_31, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGRT_32, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGABRT, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGIO, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGSYS, NULL, {SIG_DFL, [], 0}, 8) = 0
write(4, "Here's some text\n", 17)      = 17
close(4)                                = 0
close(3)                                = 0
exit_group(0)                           = ?

Any ideas about why it's not producing output? A bash script can echo text to standard out just fine.

When I run the script in debug mode it does print output.

After executing perl -v at the command line the exit code from $? was 0.

Executing

perl -e'print "foo" or die $!' 

gave and exit code of 9, but that appears to be due to the die. perl -v > file did not write anything to file.

Here is the output of stat STDOUT and the command used to write it to a file:

45826|261126|33188|1|1001|1004|0|0|1461024408|1461035504|1461035504|4096|0

perl -e 'open my $FH, ">file"; print $FH join "|", stat STDOUT '

Answer 1

Before starting reading have a look at the output of this command. Everything is pointing to STDOUT pointing to the incorrect place.

ls -l /proc/$$/fd/{1,2}

On my system I get this, note it does change as I write this because this was not written in one go.

lrwx------ 1 root root 64 May  3 17:01 /proc/27806/fd/1 -> /dev/pts/1
lrwx------ 1 root root 64 May  3 17:01 /proc/27806/fd/2 -> /dev/pts/1

I suspect the above to be similar for you. The stat looks suspicious to me, if I had access to the filesytem I'd search for the inode that it's telling me its writing to ie.

sudo find / -printf "%i:\t%p\n"|grep 261126

If when Perl starts it's changing it's stdout etc to the wrong place I'd add a very long sleep to the script then do the search to see where it is. If the file is a regular file and it's on the filesystem this should find it.

My stat on STDOUT

|dev   |inode  |mode  |link |uid |gid |rdev |size |atime     |mtime     |ctime     |blk |blka
|13    |3      |8592  |1    |1000|5   |34816|0    |1462301986|1462301986|1462301958|1024|0

Your stat on STDOUT

|dev   |inode  |mode  |link |uid |gid |rdev |size |atime     |mtime     |ctime     |blk |blka
|45826 |261126 |33188 |1    |1001|1004|0    |0    |1461024408|1461035504|1461035504|4096|0

On mine my dev has minor number 13 and looks ok when I search for it under devices. If we mask yours off to show major/minor you have...

major == 179
minor == 2

Note, I originally had these in reverse until corrected by Wumpus Q. Wumbley.

On my machine this is

crw-------  1 root  root   2, 179 Apr 29 12:50 ptya3

On mine my rdev equates to

major == 136 
minor == 0

On my Debian system this is /dev/pts/0. Your rdev is 0. I had a quick look round and some people using screen can have problems with /dev/pts/N ie it's not there but that's me guessing.

The strace is also really odd, I got the following lines when it wrote on my system:

read(3, "#!/usr/bin/perl -w\n#use strict;\n"..., 8192) = 228
read(3, "", 8192)                       = 0
close(3)                                = 0
write(1, "Here's some text STDOUT\n", 24Here's some text STDOUT
) = 24
write(2, "Here's some text STDERR\n", 24Here's some text STDERR
) = 24
write(1, "Here's some text STDOUT\n", 24Here's some text STDOUT
) = 24

The fact that these appear no where in your strace is very strange indeed. You can change where the appear by messing around with $| but they should appear somewhere. Gilles noticed that the mode is also odd. If you run this script...

#!/usr/bin/perl
use warnings;
use strict;
use Fcntl ':mode';
my $mode = 33188;
my $user_rwx      = ($mode & S_IRWXU) >> 6;
print("user_rwx      = $user_rwx\n");
my $group_read    = ($mode & S_IRGRP) >> 3;
print("group_read    = $group_read\n");
my $other_execute    =  $mode & S_IXOTH;
print("other_execute = $other_execute\n");
printf "Permissions are %04o\n", S_IMODE($mode), "\n";
my $is_setuid     =  $mode & S_ISUID;
print("is_setuid     = $is_setuid\n");
my $is_directory  =  S_ISDIR($mode);
print("dir           = $is_directory\n");
my $is_reg  = S_ISREG($mode);
print("regular       = $is_reg\n");

You can see that STDOUT appears to be pointing at a regular file. This would confirm why rdev is zero ie if stdout was redirecting to something that was meant to be a device but actually was just a normal file. I've seen odd things like that happen in chrooted environments where devices were not setup properly.

Regardless of buffering being on or off on exit the buffers should have have been flushed ie you would see calls to the write sys call. It's really weird that there are no writes at all in the strace.