shell script q's (io, error exiting )
 

Hi
I have a few questions about bash scripting.

1. how can i send output to stdout and redirect same output to a log file in the same line of code ??

2. I have a script which runs various commands and compiles programs, whats the most efficient piece of code to attempt to run/compile the program and in case of error to write a error message to stout, and the log and then redirect stderror to the log. In the case there is no problem i want the script to carry on running

thanks

this would send any errors during "make" to a text file:

a handy tool for your first problem is 'tee'. 'tee' takes standard input, and prints it to standard output and a file you specify. eg.

cat file.txt | tee file2.txt

by redirecting the stdout of cat to stdin of tee with a pipe, tee will write stdin to stdout and a file named file2.txt

Hi,

1) Use the tee command:

command | tee outfile : This will sent stdout to terminal and to outfile

If you want to redirect stderr to outfile too:

command 2>&1 | tee outfile

2) I'm not sure what it is you want:

Maybe the following does what you want:

command 1>/tmp/out 2>&1 || { echo "Oops..." ; cat /tmp/out ; exit 1 ; }
command2

The output (stdout and stderr) is redirected to /tmp/out. If command fails everything after || is executed, if command is
ok then command 2 will be executed.

If the part after || is executed the following happens:

An 'error' is displayed ( echo "Oops..." ),
All the output is shown ( cat /tmp/out ), remember both stderr and stdout are in this file,
The script exits with an appropriate exit code (1 in this case).

Hope this helps.

Hi, thanks for the replies :) -especially druuma

Finally i used tee with echo and ||. Just as a side note what do you all use for shell scripting ?? Im using vim now, but debugging is a pain, what do you all recommend ?

Hi,

I'm a vi(m) addict, so there's nothing else for me :)

To make life a bit easier you can (if it isn't already) turn on syntax support and highlighting in vim. It's not real dubugging, but it does show incomplete/wrong syntax while you type.

The set -x switch that comes with bash/ksh can also help during test execution of the new script.

Again, hope this helps.

If i'm really stuck on a bash script I use
set -xv
at the top:
-v Print shell input lines as they are read.
-x After expanding each simple command, for command, case
command, select command, or arithmetic for command,
display the expanded value of PS4, followed by the com-
mand and its expanded arguments or associated word
list.