I'm writing a Bash Script and in it I execute a piped command within a Function I wrote and I can't seem to redirect the
stderr from the 1st pipe to stdout..?
I'm setting the output to an Array "COMMAND_OUTPUT" and splitting on newlines using this --> "( $(...) )". By putting
the extra ( ) around the $( ), it splits the output using the IFS and sets the array elements.
Then the command after the semi-colon echos BOTH Return Codes from each command using the PIPESTATUS Array
Variable to STDOUT. which works perfectly getting the Return Codes.
I've tried adding "2>&1" to each point in the Command within "$(..)", but none seem to send the 'cat' command's STDERR
to STDOUT in order to capture the error inside the Array "COMMAND_OUTPUT".
If I set $SEND_FILE to a file that doesn't Exist, I can see that everything gets stored in the COMMAND_OUTPUT Array
except for "cat: : No such file or directory". Which get printed immediately when that line is executed.
Any ideas on how to redirect the stderr from the 1st pipe command to stdout? Any thoughts would be much appreciated!
Subshell is great for low effort logging "(...) >>log_file 2>&1" as it allows you to concatenate stdout and or stderr on multiple commands and split stdin if you use whole-line or all-one-shell commands, like line, below. The 'tail -1' would not work, for the stdin FILE* buffer would swallow the second and some following line parts that would be lost when tail exited, but 'line' does a lot of read(0,*buf,1) until it finds a linefeed, so the second line is still left within/behind the fd, which is inherited, not the FILE*.
Code:
$ ps -el |(
line
sort -nr +9
)|pg
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME COMD
1 R 0 25915 1 0 152 20 c0b8ef00 15155 - ? 18:17 mad
401 R 0 2043 2041 0 152 20 a49f4000 13600 - ? 24:59 java
1 S 6068 10960 1 0 154 20 a6c0ed00 12881 c0e470 ? 1:07 xterm
1 S 6068 12264 1 1 154 20 a4603f00 10437 c0e470 ? 0:24 xterm
1 S 6068 11882 1 0 154 20 a733d300 10437 c0e470 ? 0:17 xterm
1 S 0 1600 1 0 127 20 a2a2a300 5754 b9006f00 ? 20:38 scopeux
401 R 37288 7220 7219 0 152 20 a724d000 5391 - ? 26:51 java
141 R 0 1566 1 0 -16 20 a2a54700 4827 - ? 138:40 midaemon
401 R 0 1274 1 0 152 20 a18f7f00 4362 - ? 27:32 java
1 S 6068 11490 1 0 154 20 a7f97600 4185 c0e470 ? 0:00 xterm
1 S 6068 11145 1 0 154 20 a8feba00 4185 c0e470 ? 0:01 xterm
If I move the command to a new Function and simply execute the command only inside the function and then set the function call to a variable
and redirect to stderr from the function call, it will then redirect stderr to stdout.
Like this:
Code:
execute_command()
{
local FILE="$1"
cat "$FILE" | send_nsca $IPADDR -p 5667 -to 10 -d , -c $SEND_NSCA_CFG
EXIT_CODES="${PIPESTATUS[@]}"
echo "EXIT_CODES=$EXIT_CODES"
}
IFS="
"
# Redirecting HERE, at Function call will send STDERR to STDOUT and array now holds all messages from the
# command, including the "EXIT_CODES=1 0"
COMMAND_OUTPUT=( $(execute_command "$SEND_FILE" 2>&1) )
echo -ne "COMMAND_OUTOUT:\n"
echo -ne "${COMMAND_OUTPUT[*]}\n\n"
Now this way sends STDERR to STDOUT and the Array now holds all the data (including stderr)...
Is this a bad way to do this, or is that ok to do?
Thanks Again,
Matt
---------- Post updated at 05:11 PM ---------- Previous update was at 05:09 PM ----------
Hey DGPickett, thanks for the reply!
Cool, thanks for the example... Much appreciated!
I was about to head out for the day, I'll probably pick back up on this tomorrow or Monday... Need to clear my head a bit!
Thanks guys for ALL your replies!
I'll be sure to give BGPickett's example a try.
I had to remove the 2nd "2>&1" that was right after the 'cat' Command in order to get its STDERR to be captured by the
array "COMMAND_OUTPUT"... But other then that it worked PERFECTLY..!
Final code to capture both Command's STDERR & STDOUT into an Array:
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