UNIX for Dummies Questions & Answers

I have to confirm that an engine was not able to run. In the output below you see that it indeed got errors, but it didn't send those messages to the output file. When I run the same thing with a different executable it works. So does this mean something in the executable could cause it not to go to the output file??

$ cd Tar
$ ./Engine > ../engine_output.txt
exec(): 0509-036 Cannot load program ./Engine because of the following errors:
0509-150 Dependent module libodbc.a(libodbc.so.1) could not be loaded.
0509-022 Cannot load module libodbc.a(libodbc.so.1).
0509-026 System error: A file or directory in the path name does not exist.
$ cd ..
$ cat engine_output.txt
$ ls
AIX_50_ODBC_test.sh engine.tar engine_result.txt
Tar engine_output.txt
$

The errors are going to stderr (2) Normal output goes to stdout (1)

Code:

$ ./Engine 2>&1 > ../engine_output.txt

This makes both streams go to ../engine_output.txt

It won't make both streams go to the file becasue 2 is duplicated to 1 before 1 is redirected to the file. As a result stdout goes to the file and stderr goes to stdout.

Code:

$ ./Engine > ../engine_output.txt 2>&1

You're correct, but as far as this code goes, both streams end up written to to log file.

I disagree:

Code:

#!/bin/ksh
#
# test.sh : demonstrate redirection
#
#
echo "I am stdout"
echo "I am stderr" >&2

Code:

# ./test.sh > log1
I am stderr
# cat log1
I am stdout

Code:

# ./test.sh 2>&1 > log2
I am stderr
# cat log2
I am stdout

Code:

# ./test.sh > log3 2>&1
# cat log3
I am stdout
I am stderr

The order of redirection is important because if the duplication happens from 2 to 1 before redirection of 1, error output is redirected to fd1 ( stdout ) and standard output is redirected elsewhere. On the other hand if it happens afterwards the duplication is to "the same place as standard output"

Thanks guys. This helps alot.

This works for all my normal executions. But on one machine, a coredump is expected on one command. We don't care, just need to confirm the version info. This is output from the exe:

$ ./Up


-*-*- XXXXXXX UPDATE XXXXX Version nnnnnnnn -*-*-
-*-*- Copyright (C) 1998-2007 xxxxxxxxxxxxxx, Inc. -*-*-

Processing begins: 10/4/2007 10:48:12

Tracking Database Connect Error
Memory fault(coredump)

However, when I send the output to a file, the output file is empty:

$ ./Up > ../Up_output.txt 2>&1
Memory fault(coredump)
$ cd ..
$ cat Up_output.txt
$