redirecting BASH script stdout/stderr from the script itself

Hewson · 04-18-2008, 01:44 PM

Hi all.

I need to have stdout and stderr sent both to stdout and to a file, the file needs to be unique everytime. The unique id is not known until the script is run. (in production the id will be a SQL unique key, but for simplicty sake lets just say its the PID of the script itself)

Contents of helloworld.sh

Code:

#!/bin/bash
 #create outputfile
fileName="hello_world$$.log"
 # this is wrong.  it will only redirect the output of that line.
 # i need something that will work for the rest of the script from here on out.
2>&1 | tee $fileName

echo "hello world"

execution of helloworld.sh

Code:

[hewson@chives test]$ ./helloworld.sh
hello world
[hewson@chives test]$ cat hello_world23186.log
[hewson@chives test]$

GrapefruiTgirl · 04-18-2008, 02:23 PM

Surely there are Bashier folks out there than I, but I have just done basically like you do, but do it on every line where the output has to go to the log.
But at the start, I would define the log:

LOG=/path/to/filename.log

then just end each line with "2>&1 | tee $LOG"

Another way, would be to (break the script into a little piece, and a big piece) use the little piece to create (or otherwise determine) the logfile name, then either:
1) export it, and run the second half of the script like ./script 2>&1 | tee $EXPORTED_LOGNAME
or
2) the first part catches/creates the logfile name same as above, but then calls the second half itself, from within, directing (tee'ing) all output to logfilename same as above:

# first script
LOG=/path/to/log.log
# call 2nd script:
/script_no2 2>&1 | tee $LOG

Any use?

Hope it gives you ideas, at least!

Sasha

Hewson · 04-18-2008, 03:06 PM

Quote:

Originally Posted by GrapefruiTgirl

Surely there are Bashier folks out there than I, but I have just done basically like you do, but do it on every line where the output has to go to the log.
But at the start, I would define the log:

LOG=/path/to/filename.log

then just end each line with "2>&1 | tee $LOG"

Sasha,

Thanks for the response.

My script is around 400 lines, that simply won't work for me.

Quote:

Originally Posted by GrapefruiTgirl

Another way, would be to (break the script into a little piece, and a big piece) use the little piece to create (or otherwise determine) the logfile name, then either:
1) export it, and run the second half of the script like ./script 2>&1 | tee $EXPORTED_LOGNAME
or
2) the first part catches/creates the logfile name same as above, but then calls the second half itself, from within, directing (tee'ing) all output to logfilename same as above:

# first script
LOG=/path/to/log.log
# call 2nd script:
/script_no2 2>&1 | tee $LOG

I was thinking something along the same lines, but I was hoping I wouldn't have to do this.

All the same, thanks for the reply!

-Hewson

colucix · 04-18-2008, 03:21 PM

Maybe I'm not a "bashier folk"

anyway you can simply use exec to redirect both standard output and standard error of all commands in a script:

Code:

#!/bin/bash
logfile=$$.log
exec > $logfile 2>&1

GrapefruiTgirl · 04-18-2008, 03:32 PM

@ colucix--

Awesome! we both thank you; I had no idea

(You ARE bashier than I

)