i want to implement a shell-script that runs the command xyz and stores its output in a variable, but at the same time forwarding the commands output to the shell-scripts stdout.
This is because I want to launch this script via launchd, let it automatically log the script's output, but then also let the script push the individual commands output to the web. The script should not simply buffer the commands output and print it after it ran, but rather in real time.
Is something like this possible, and if, how do you implement it?
Thanks
thel30n
you are looking for the command:
$VAR=$(echo 'test' | tee /dev/tty)
test
echo $VAR
test
I believe there is no way to save log into a shell variable and avoid buffering command's output at the same time. But the alternative way would be saving log messages to a file using tee(1). For example:
LOGFILE=/path/to/logfile
run_and_log() {
$# | tee -a "$LOGFILE"
}
run_and_log xyz
Related
I am writing a script that among other things runs a shell command several times. This command doesn't handle exit codes very well and I need to know if the process ended successfully or not.
So what I was thinking is to analyze the stderr to find out the word error (using grep). I know this is not the best thing to do, I'm working on it....
Anyway, the only way I can imagine is to put the stderr of that program in a variable and then use grep to well, "grep" it and throw it to another variable. Then I can see if that variable is valorized, meaning that there was an error, and do my work.
The qustion is: how can I do this ?
I don't really want to run the program inside a variable, because it has got a lot of arguments (with special characters such as backslash, quotes, doublequotes...) and it's a memory and I/O intensive program.
Awaiting your reply, thanks.
Redirect the stderr of that command to a temporary file and check if the word "error" is present in that file.
mycommand 2> /tmp/temp.txt
grep error /tmp/temp.txt
Thanks #Jdamian, this was my answer too, in the end.
I asked my principal if I can write a temp file and it allowed, so this is the end result:
... script
command to be launched -argument -other "argument" -other "other" argument 2>&1 | tee $TEMPFILE
ERRORCODE=( `grep -i error "$TEMPFILE" `)
if [ -z $ERRORCODE ] ;
then
some actions ....
I didn't tested this yet because I got some other scripts involved that I need to write before.
What I'm trying to do is:
run the command, having its stderr redirected to stdout;
using tee, have the above result printed on screen and also to the temp file;
have grep to store the string error found on the temp file (if any) in a variable called ERRORCODE;
if that variable is populated (which mean if it has been created by grep), then the script stops, quitting with status 1, else it contiunes.
What do you think ?
If you don't need the standard output:
if mycommand 2>&1 >/dev/null | grep -q error; then
echo an error occurred
fi
I know this has been asked many times, but I can find a suitable answer in my case.
I croned a backup script using rsync and would like to see all output, errors or not, from the all script commands. I must write the command inside the script itself, and do not want to see output in my shell.
I have been trying with no success. Below part of the script.
#!/bin/bash
.....
BKLOG=/mnt/backup_error_$now.txt
# Log everything to log file
# something like
exec 2>&1 | tee $BKLOG
# OR
exec &> $BKLOG
I have been adding at the script beginig all kinds of exec | tee $BKLOG with adding &>, 2>&1at various part of the command line, but all failed. I either get an empty log file or incomplete. I need to see on log file what rsync has done, and the error if script failed before syncing.
Thank you for help. My shell is zsh, so any solution in zsh is welcomed.
To redirect all the stdout/stderr to a file place this line on top of your script:
BKLOG=/mnt/backup_error_$now.txt
exec &> "$BKLOG"
I am trying to log the changes made by my script to a log file. At a very high level, my script has functions and I want to be able to log that information to a file. I used "tee -a" but that messed up the functionality in a number of ways.
Is there a simple way to achieve this task ?
Update : Corrected typo below
function1(){ ... }
function2(){ ... }
#main
function1 | tee -a /tmp/logfile
function2 | tee -a /tmp/logfile
(edited to reflect question edits)
You can incorporate the tee into the function definition:
function() { { ...<original function definition goes here>; } | tee -a output; }
so you don't need to invoke tee each time you call the function. Obviously, if the function modifies file descriptors, you will need to do a little more work. Also, keep in mind that this changes the buffering. If commands called from within function1 have a tty for their stdout, they will probably line buffer their output, but if their stdout is a pipe (which it is if you are piping to tee) the output will be block buffered. This may be the root cause of the differences you are seeing. Also, this only captures the output of one file descriptor. Perhaps you have commands writing to stderr. You will need to provide more details about the way the pipe to tee changes the behavior of the script.
I am trying to implement something which my logic says can't be done. But I need your help to understand why can't it be.
Short Version of Question
Is it possible to log stdout+stderr of a script in csh without using file redirection ( >& or tee ).
Detailed Explanation of Question
I have a requirement with a csh script (script1) where I am not allowed to use file redirection.(I will give the reason in a while)
So that means I can't use something like
echo just checking >& logfile
hence I can't use this or tee to create my logfile.
I also have a another script (script2) which is a top level script.
I can either run script1 in standalone mode or through script2.
In either case i need to create a log(stdout+stderr) of script1 in logfile.
There are two possible(but not complete) option for that
write this line in script2
./script1 >& logfile
But then I can't log script1 in logfile when script1 is run in standalone mode.
Another option is to use file redirections in script1 like this:
echo test starting >> logfile
echo test over
In this case thee are two disadvantages:
1) "test over" prints before "test starting" , i.e. the order of occurring of command logs is not certain.
2) It's tedious to put >>& after every statement if I am intending to cover whole script.
Now is there any other way,I can get what I need. That is I can run script1 without file redirection and still get to log its stdout+stderr in logfile.
You mention csh, so this may not help you. On the other had, it may motivate you to stop using csh for scripts, a task for which it is notoriously inappropriate. In sh, you can simply do:
#!/bin/sh
exec > logfile 2>&1
echo foo
To write foo (and the output and errors of all subsequent commands) to the logfile
We have scripts of following nature (in cron)
someScript.sh > /tmp/cronlog/somescript.$(date +%Y%m%d).log 2>&1
Now is there a way by which with in someScript.sh I can figure out what file the output has gone in to?
The script sends email with summary. At the same time I would like to mention that details could be found in so and so output file - with in the email.
I am aware of the construct if [ -t 1 ] to detect stdout etc but how to get the output file name?
Note that I want this to be generic so that some one can change the output file in cron and the script does not need to be modified.
The simplest thing I could think is that:
readlink -f /proc/$$/fd/1
$$ is the PID of the script (inside the script). On most unix systems, /proc/[pid] is the pseudo-directory containing info for process [pid].
/proc/[pid]/fd is a directory containing a list of symlinks for the open file-descriptors of the process. fd/0 is input, fd/1 is the output of the script, etc.
readlink then gives you the target file or tty if you don't redirect the output.
Of course, if you want to display it, you have to display it somewhere else than standard ouput, or it will be redirected! To debug, try the std error (2).
Various callings give those results on my box (script.sh just calls readlink -f /proc/$$/fd/1 >&2)
# ./script.sh
/dev/pts/0
# ./script.sh > /var/tmp/foo
/var/tmp/foo
# ./script.sh | more
/proc/12132/fd/pipe:[916212]
Rather than trying to find a hack (and that too platform dependent) its better to take a slightly different approach here.
Set your cron job like this:
someScript.sh /tmp/cronlog/somescript.$(date +%Y%m%d).log
i.e. without and > or 2>&1 (stdout/stderr streams redirections) and just pass an argument with the desired logfile name.
Now inside someScript.sh redirect streams to your log file like this:
LOGFILE=$1
exec &>${LOGFILE}
And finally you can then message your clients that:
"output details could be found in ${LOGFILE}"