Is there a way for a script to log both, the command line run (including piped ones) plus its output without duplicating the line for the command?
The intention is that the script should have a clean output, but should log verbosely into a log file (so no set -x). Apart from the output, it shall also log the command line causing the output, which could be a piped command-one liner.
The most basic approach is to duplicate the command line in the script and then dump it into the log followed by the captured output of the actual command being run:
echo "command argument1 \"quoted argument2\" | grep -oE \"some output\"" >> file.log
output="$(command argument1 "quoted argument2" 2>&1 | grep -oE "some output")"
echo "${output}" >> file.log
This has the side effect that quoted sections would need to be escaped for the log, which can lead to errors resulting in confusion.
If none of the commands were piped, one could store the command line in an array and then "run" the array.
command=(command argument1 "quoted argument2")
echo "${command[#]}" >> file.log
output="$("${command[#]}" 2>&1)"
echo "${output}" >> file.log
Though with this approach "quoted argument2" would become quoted argument2 in the log.
Is there a way (in bash) to realize this without having to duplicate the commands?
You could play with redirections, switch the x option on and off on demand, unset PS4 to get rid of the leading + , and define log_on and log_off functions for easier coding. Something like this:
$ cat script.sh
#!/usr/bin/env bash
function log_on {
exec 3>&1 4>&2
exec &> >( sed -E '/^(set \+x|log_off)$/d' >> file.log )
ps4=$PS4
PS4=
set -x
}
function log_off {
set +x
exec 1>&3 2>&4
PS4=$ps4
}
echo something not logged
log_on
echo something logged
log_off
echo something else not logged
$ rm -f file.log
$ ./script.sh
something not logged
something else not logged
$ cat file.log
echo something logged
something logged
The exec <redirection> commands look a bit cryptic (as most redirections) but they are rather simple:
exec 3>&1 4>&2 makes copies of file descriptors fd1 and fd2 (stdout and stderr by default) to be able to restore these in log_off. After this fd3 and fd4 are copies of fd1 and fd2, respectively. Pick other fd than 3 or 4 if you already use them.
exec &> >( sed ... ) redirect fd1 and fd2 to the standard input of a sed command.
The sed command sed -E '/^(set \+x|log_off)$/d' >> file.log deletes lines containing only set + or log_off and appends its output to file.log. Without this sed command you would always see the two following lines:
log_off
set +x
in your logs, after a group of logged commands.
exec 1>&3 2>&4 restores fd1 and fd2 from their copies in fd3 and fd4.
The rest is straightforward: save PS4 in ps4 such that it can be restored, enable/disable the x option. This should be easy to adapt or extend if needed.
The x option displays the simple commands separately. It breaks pipes, for instance. If you prefer a command log that looks more like the commands you wrote you can replace set -/+x by set -/+v.
IMHO this has already been answered here:
For simplicity the set linux command is what you need.
set -x or set -v
I'm trying to redirect a program's stdin and stdout. I'm currently experimenting with a bash mockup of this, but I'm getting some odd behavior.
I have the following:
mkfifo in
mkfifo out
I also have the following script, test.sh
#!/bin/bash
while read line; do
echo "I read ${line}"
done < /dev/stdin
In terminal 1, I do the following:
tail -f out
In terminal 2, I do the following:
./test.sh < in > out
In terminal 3, I do the following:
echo "foo" > in
echo "bar > in
However, instead of seeing "I read foo" followed by "I read bar" in terminal 1, I get nothing after the first echo, both lines after the second echo, and then the test.sh program in terminal 2 exits. How can I prevent the exit so I can keep sending test.sh input? Also, instead of buffering and then dumping when the program terminates, how can I get the output from test.sh to flush to the tail -f in terminal 1?
Use the redirection on a single compound command that contains your two echo commands.
{
echo "foo"
echo "bar"
} > in
If, as seems likely on a closer reading, you want in to stay open while you are executing commands interactively, use exec to open in on another file descriptor:
exec 3> in # Open in on file descriptor 3
echo "foo" >&3 # Write to file descriptor 3 instead of standard output
echo "bar" >&3 # "
exec 3>&- # Close file descriptor 3
Note that exec 3> in will block until something (test.sh in your case) opens in for reading, and due to buffering, you may not see any output from tail -f out until you close file descriptor 3.
I have been trying to get a bash script to output different things on the terminal and logfile but am unsure of what command to use.
For example,
#!/bin/bash
freespace=$(df -h / | grep -E "/" | awk '{print $4}')
greentext="\033[32m"
bold="\033[1m"
normal="\033[0m"
logdate=$(date +"%Y%m%d")
logfile="$logdate"_report.log
exec > >(tee -i $logfile)
echo -e $bold"Quick system report for "$greentext"$HOSTNAME"$normal
printf "\tSystem type:\t%s\n" $MACHTYPE
printf "\tBash Version:\t%s\n" $BASH_VERSION
printf "\tFree Space:\t%s\n" $freespace
printf "\tFiles in dir:\t%s\n" $(ls | wc -l)
printf "\tGenerated on:\t%s\n" $(date +"%m/%d/%y") # US date format
echo -e $greentext"A summary of this info has been saved to $logfile"$normal
I want to omit the last output (echo "A summary...") in the logfile while displaying it in the terminal. Is there a command to do so? It would be great if a general solution can be provided instead of a specific one because I want to apply this to other scripts.
EDIT 1 (after applying >&6):
Files in dir: 7
A summary of this info has been saved to 20160915_report.log
Generated on: 09/15/16
One option:
exec 6>&1 # save the existing stdout
exec > >(tee -i $logfile) # like you had it
#... all your outputs
echo -e $greentext"A summary of this info has been saved to $logfile"$normal >&6
# writes to the original stdout, saved in file descriptor 6 ------------^^^
The >&6 sends echo's output to the saved file descriptor 6 (the terminal, if you're running this from an interactive shell) rather than to the output path set up by tee (which is on file descriptor 1). Tested on bash 4.3.46.
References: "Using exec" and "I/O Redirection"
Edit As OP found, the >&6 message is not guaranteed to appear after the lines printed by tee off stdout. One option is to use script, e.g., as in the answers to this question, instead of tee, and then print the final message outside of the script. Per the docs, the stdbuf answers to that question won't work with tee.
Try a dirty hack:
#... all your outputs
echo >&6 # <-- New line
echo -e $greentext ... >&6
Or, equally hackish, (Note that, per OP, this worked)
#... all your outputs
sleep 0.25s # or whatever time you want <-- New line
echo -e ... >&6
I have sophisticated bash script that uses "read -p"(stderr output) very often. And now I need to duplicate all script input from terminal into log file.
tee file.log | script.sh
this command does'nt work carefully because ignores output to user.
Example:
#!/bin/sh
echo "start"
read -p "input value: " val
echo $val
echo "finish"
Terminal run:
start
input value: 3
3
finish
Tee run:
# tee file.log | ./script.sh
start
3
3
finish
No idea why you're using tee here. What I suspect is happening is it needs input, so waits for it, then pipes 3 to stdout
-p prompt
Display prompt, without a trailing newline, before attempting
to read any input. The prompt is displayed only if input is coming from a
terminal.
However input isn't sent from tty here so prompt is never printed. Still feels very weird for me to use tee here, but you can just use echo -n instead of the -p flag for read and it should work.
#!/bin/sh
echo "start"
echo -n "input value: "
read val
echo $val
echo "finish"
e.g.
> tee file.log | ./abovescript
start
input value: 3
3
finish
> cat file.log
3
Also not sure how to get tee to terminate properly from in-script here, so you need to press return key at end which of course causes newline.
That said, since it's an extra line each time anyway, seems worse than just be doing echo "$val" >> file.log each time, though a better option would be just to use a function
#!/bin/bash
r() {
read -p "input value: " val
echo "$val" >> file.log
echo "$val"
}
echo "start"
val=$(r)
echo "$val"
echo "finish"
I know how to use tee to write the output (standard output) of aaa.sh to bbb.out, while still displaying it in the terminal:
./aaa.sh | tee bbb.out
How would I now also write standard error to a file named ccc.out, while still having it displayed?
I'm assuming you want to still see standard error and standard output on the terminal. You could go for Josh Kelley's answer, but I find keeping a tail around in the background which outputs your log file very hackish and cludgy. Notice how you need to keep an extra file descriptor and do cleanup afterward by killing it and technically should be doing that in a trap '...' EXIT.
There is a better way to do this, and you've already discovered it: tee.
Only, instead of just using it for your standard output, have a tee for standard output and one for standard error. How will you accomplish this? Process substitution and file redirection:
command > >(tee -a stdout.log) 2> >(tee -a stderr.log >&2)
Let's split it up and explain:
> >(..)
>(...) (process substitution) creates a FIFO and lets tee listen on it. Then, it uses > (file redirection) to redirect the standard output of command to the FIFO that your first tee is listening on.
The same thing for the second:
2> >(tee -a stderr.log >&2)
We use process substitution again to make a tee process that reads from standard input and dumps it into stderr.log. tee outputs its input back on standard output, but since its input is our standard error, we want to redirect tee's standard output to our standard error again. Then we use file redirection to redirect command's standard error to the FIFO's input (tee's standard input).
See Input And Output
Process substitution is one of those really lovely things you get as a bonus of choosing Bash as your shell as opposed to sh (POSIX or Bourne).
In sh, you'd have to do things manually:
out="${TMPDIR:-/tmp}/out.$$" err="${TMPDIR:-/tmp}/err.$$"
mkfifo "$out" "$err"
trap 'rm "$out" "$err"' EXIT
tee -a stdout.log < "$out" &
tee -a stderr.log < "$err" >&2 &
command >"$out" 2>"$err"
Simply:
./aaa.sh 2>&1 | tee -a log
This simply redirects standard error to standard output, so tee echoes both to log and to the screen. Maybe I'm missing something, because some of the other solutions seem really complicated.
Note: Since Bash version 4 you may use |& as an abbreviation for 2>&1 |:
./aaa.sh |& tee -a log
This may be useful for people finding this via Google. Simply uncomment the example you want to try out. Of course, feel free to rename the output files.
#!/bin/bash
STATUSFILE=x.out
LOGFILE=x.log
### All output to screen
### Do nothing, this is the default
### All Output to one file, nothing to the screen
#exec > ${LOGFILE} 2>&1
### All output to one file and all output to the screen
#exec > >(tee ${LOGFILE}) 2>&1
### All output to one file, STDOUT to the screen
#exec > >(tee -a ${LOGFILE}) 2> >(tee -a ${LOGFILE} >/dev/null)
### All output to one file, STDERR to the screen
### Note you need both of these lines for this to work
#exec 3>&1
#exec > >(tee -a ${LOGFILE} >/dev/null) 2> >(tee -a ${LOGFILE} >&3)
### STDOUT to STATUSFILE, stderr to LOGFILE, nothing to the screen
#exec > ${STATUSFILE} 2>${LOGFILE}
### STDOUT to STATUSFILE, stderr to LOGFILE and all output to the screen
#exec > >(tee ${STATUSFILE}) 2> >(tee ${LOGFILE} >&2)
### STDOUT to STATUSFILE and screen, STDERR to LOGFILE
#exec > >(tee ${STATUSFILE}) 2>${LOGFILE}
### STDOUT to STATUSFILE, STDERR to LOGFILE and screen
#exec > ${STATUSFILE} 2> >(tee ${LOGFILE} >&2)
echo "This is a test"
ls -l sdgshgswogswghthb_this_file_will_not_exist_so_we_get_output_to_stderr_aronkjegralhfaff
ls -l ${0}
In other words, you want to pipe stdout into one filter (tee bbb.out) and stderr into another filter (tee ccc.out). There is no standard way to pipe anything other than stdout into another command, but you can work around that by juggling file descriptors.
{ { ./aaa.sh | tee bbb.out; } 2>&1 1>&3 | tee ccc.out; } 3>&1 1>&2
See also How to grep standard error stream (stderr)? and When would you use an additional file descriptor?
In bash (and ksh and zsh), but not in other POSIX shells such as dash, you can use process substitution:
./aaa.sh > >(tee bbb.out) 2> >(tee ccc.out)
Beware that in bash, this command returns as soon as ./aaa.sh finishes, even if the tee commands are still executed (ksh and zsh do wait for the subprocesses). This may be a problem if you do something like ./aaa.sh > >(tee bbb.out) 2> >(tee ccc.out); process_logs bbb.out ccc.out. In that case, use file descriptor juggling or ksh/zsh instead.
To redirect standard error to a file, display standard output to the screen, and also save standard output to a file:
./aaa.sh 2>ccc.out | tee ./bbb.out
To display both standard error and standard output to screen and also save both to a file, you can use Bash's I/O redirection:
#!/bin/bash
# Create a new file descriptor 4, pointed at the file
# which will receive standard error.
exec 4<>ccc.out
# Also print the contents of this file to screen.
tail -f ccc.out &
# Run the command; tee standard output as normal, and send standard error
# to our file descriptor 4.
./aaa.sh 2>&4 | tee bbb.out
# Clean up: Close file descriptor 4 and kill tail -f.
exec 4>&-
kill %1
If using Bash:
# Redirect standard out and standard error separately
% cmd >stdout-redirect 2>stderr-redirect
# Redirect standard error and out together
% cmd >stdout-redirect 2>&1
# Merge standard error with standard out and pipe
% cmd 2>&1 |cmd2
Credit (not answering from the top of my head) goes here: Re: bash : stderr & more (pipe for stderr)
If you're using Z shell (zsh), you can use multiple redirections, so you don't even need tee:
./cmd 1>&1 2>&2 1>out_file 2>err_file
Here you're simply redirecting each stream to itself and the target file.
Full example
% (echo "out"; echo "err">/dev/stderr) 1>&1 2>&2 1>/tmp/out_file 2>/tmp/err_file
out
err
% cat /tmp/out_file
out
% cat /tmp/err_file
err
Note that this requires the MULTIOS option to be set (which is the default).
MULTIOS
Perform implicit tees or cats when multiple redirections are attempted (see Redirection).
Like the accepted answer well explained by lhunath, you can use
command > >(tee -a stdout.log) 2> >(tee -a stderr.log >&2)
Beware than if you use bash you could have some issue.
Let me take the matthew-wilcoxson example.
And for those who "seeing is believing", a quick test:
(echo "Test Out";>&2 echo "Test Err") > >(tee stdout.log) 2> >(tee stderr.log >&2)
Personally, when I try, I have this result:
user#computer:~$ (echo "Test Out";>&2 echo "Test Err") > >(tee stdout.log) 2> >(tee stderr.log >&2)
user#computer:~$ Test Out
Test Err
Both messages do not appear at the same level. Why does Test Out seem to be put like if it is my previous command?
The prompt is on a blank line letting me think the process is not finished, and when I press Enter this fix it.
When I check the content of the files, it is ok, and redirection works.
Let’s take another test.
function outerr() {
echo "out" # stdout
echo >&2 "err" # stderr
}
user#computer:~$ outerr
out
err
user#computer:~$ outerr >/dev/null
err
user#computer:~$ outerr 2>/dev/null
out
Trying again the redirection, but with this function:
function test_redirect() {
fout="stdout.log"
ferr="stderr.log"
echo "$ outerr"
(outerr) > >(tee "$fout") 2> >(tee "$ferr" >&2)
echo "# $fout content: "
cat "$fout"
echo "# $ferr content: "
cat "$ferr"
}
Personally, I have this result:
user#computer:~$ test_redirect
$ outerr
# stdout.log content:
out
out
err
# stderr.log content:
err
user#computer:~$
No prompt on a blank line, but I don't see normal output. The stdout.log content seem to be wrong, and only stderr.log seem to be ok.
If I relaunch it, the output can be different...
So, why?
Because, like explained here:
Beware that in bash, this command returns as soon as [first command] finishes, even if the tee commands are still executed (ksh and zsh do wait for the subprocesses)
So, if you use Bash, prefer use the better example given in this other answer:
{ { outerr | tee "$fout"; } 2>&1 1>&3 | tee "$ferr"; } 3>&1 1>&2
It will fix the previous issues.
Now, the question is, how to retrieve exit status code?
$? does not work.
I have no found better solution than switch on pipefail with set -o pipefail (set +o pipefail to switch off) and use ${PIPESTATUS[0]} like this:
function outerr() {
echo "out"
echo >&2 "err"
return 11
}
function test_outerr() {
local - # To preserve set option
! [[ -o pipefail ]] && set -o pipefail; # Or use second part directly
local fout="stdout.log"
local ferr="stderr.log"
echo "$ outerr"
{ { outerr | tee "$fout"; } 2>&1 1>&3 | tee "$ferr"; } 3>&1 1>&2
# First save the status or it will be lost
local status="${PIPESTATUS[0]}" # Save first, the second is 0, perhaps tee status code.
echo "==="
echo "# $fout content :"
echo "<==="
cat "$fout"
echo "===>"
echo "# $ferr content :"
echo "<==="
cat "$ferr"
echo "===>"
if (( status > 0 )); then
echo "Fail $status > 0"
return "$status" # or whatever
fi
}
user#computer:~$ test_outerr
$ outerr
err
out
===
# stdout.log content:
<===
out
===>
# stderr.log content:
<===
err
===>
Fail 11 > 0
In my case, a script was running command while redirecting both stdout and stderr to a file, something like:
cmd > log 2>&1
I needed to update it such that when there is a failure, take some actions based on the error messages. I could of course remove the dup 2>&1 and capture the stderr from the script, but then the error messages won't go into the log file for reference. While the accepted answer from lhunath is supposed to do the same, it redirects stdout and stderr to different files, which is not what I want, but it helped me to come up with the exact solution that I need:
(cmd 2> >(tee /dev/stderr)) > log
With the above, log will have a copy of both stdout and stderr and I can capture stderr from my script without having to worry about stdout.
The following will work for KornShell (ksh) where the process substitution is not available,
# create a combined (standard input and standard output) collector
exec 3 <> combined.log
# stream standard error instead of standard output to tee, while draining all standard output to the collector
./aaa.sh 2>&1 1>&3 | tee -a stderr.log 1>&3
# cleanup collector
exec 3>&-
The real trick here, is the sequence of the 2>&1 1>&3 which in our case redirects the standard error to standard output and redirects the standard output to file descriptor 3. At this point the standard error and standard output are not combined yet.
In effect, the standard error (as standard input) is passed to tee where it logs to stderr.log and also redirects to file descriptor 3.
And file descriptor 3 is logging it to combined.log all the time. So the combined.log contains both standard output and standard error.
Thanks lhunath for the answer in POSIX.
Here's a more complex situation I needed in POSIX with the proper fix:
# Start script main() function
# - We redirect standard output to file_out AND terminal
# - We redirect standard error to file_err, file_out AND terminal
# - Terminal and file_out have both standard output and standard error, while file_err only holds standard error
main() {
# my main function
}
log_path="/my_temp_dir"
pfout_fifo="${log_path:-/tmp}/pfout_fifo.$$"
pferr_fifo="${log_path:-/tmp}/pferr_fifo.$$"
mkfifo "$pfout_fifo" "$pferr_fifo"
trap 'rm "$pfout_fifo" "$pferr_fifo"' EXIT
tee -a "file_out" < "$pfout_fifo" &
tee -a "file_err" < "$pferr_fifo" >>"$pfout_fifo" &
main "$#" >"$pfout_fifo" 2>"$pferr_fifo"; exit
Compilation errors which are sent to standard error (STDERR) can be redirected or save to a file by:
Bash:
gcc temp.c &> error.log
C shell (csh):
% gcc temp.c |& tee error.log
See: How can I redirect compilation/build error to a file?