I can I echo error message and send it into a log file? - linux

I'm trying to echo the error message as well as writing it in a log file at the same time but I'm not sure how to do it. I've used 1>&2, but it just sends it to the log file and doesn't echo the message. Here's my code:
while read -r username password; do
egrep "^$username" /etc/passwd >/dev/null
if [ $? -eq 0 ]; then
echo "ERROR BLABLAH $DATE" 1>&2 >> /var/log/error.log

Try
echo "ERROR BLABLAH $DATE" | tee -a /var/log/error.log 1>&2
Description:
tee # will repeat the std input.
-a /var/log/error.log # will append to the error.log file
1>&2 # will send the stdin to stderr.

You want to use the 'tee' command:
NAME
tee - read from standard input and write to standard output
and files
SYNOPSIS
tee [OPTION]... [FILE]...
e.g.
$echo "Hello world!" | tee test.txt
Hello world!
$cat test.txt
Hello world!

Related

WHOIS BASH Script sometimes not fetching data

My whois bash script works for a few domains and doesn't for others.
When I run the command directly in my terminal for the same domain, I am able to see output. Also, sometimes the script will not run properly and gets stuck, then I need to interrupt that.
Why is that, and how can I fix it?
Let's say the domain.txt file contains: gmail.com, zoom.us, facebook.com, bank.com etc.
The script is:
#!/bin/bash
echo "Please enter the full path of txt file"
read path
filename=$path
while read line
do
echo "Checking domain $line"
a=$(whois $line | grep -i -e "Creation Date" | head -1)
b=$(whois $line | grep -i -e "no match" | head -1)
echo "$a"$line >> /root/outputdomain.csv
done <$filename
echo "file has been processed successfully."
A sample input txt file is:
linkedin.com
zoom.us
sbi.co.in
facebook.com
sap.com
hsbc.com
Expected Output is:
Creation Date: 2002-11-02T15:38:11Z linkedin.com
Creation Date: 2002-04-24T15:03:39Z zoom.us
Whats is working for me currently:
Creation Date: 2002-11-02T15:38:11Z linkedin.com
Creation Date: 1997-03-29T05:00:00Z facebook.com
But no output for zoom.us, sbi.co.in.
If I run the command below, I am able to fetch the required data:
$ whois zoom.us | grep -E "Creation Date" | head -1
Creation Date: 2002-04-24T15:03:39Z
I don't use/know whois but base on your post this is what I came up with.
#!/usr/bin/env bash
shopt -s extglob
echo "Please enter the full path of txt file"
read -r path
filename=$path
while read -r line; do
printf 'Processing %s\n' "$line"...
if a=$(whois "$line" | grep --line-buffer -Fi -m1 "creation date"); then
printf '%s %s\n' "${a##*+([[:blank:]])}" "$line" >> outputdomain.csv
else
printf '%s No domain match\n' "$line" >> outputdomain.csv
fi
sleep 5
done < "$filename"
-m Might not be POSIX but it is in GNU and BSD grep.

output of shell script to console and file

I have shell script in Linux like below
#!/bin/bash
LOG_LOCATION=/home/$USER/logs
exec > >(tee /home/$USER/logs/"$1") 2>&1
[ $# -ne 1 ] && { echo "Usage : $0 table ";exit 1; }
table=$1
TIMESTAMP=`date "+%Y-%m-%d"`
touch /home/$USER/logs/${TIMESTAMP}.success_log
touch /home/$USER/logs/${TIMESTAMP}.fail_log
success_logs=/home/$USER/logs/${TIMESTAMP}.success_log
failed_logs=/home/$USER/logs/${TIMESTAMP}.fail_log
#Function to get the status of the job creation
function log_status
{
status=$1
message=$2
if [ "$status" -ne 0 ]; then
echo "`date +\"%Y-%m-%d %H:%M:%S\"` [ERROR] $message [Status] $status : failed" | tee -a "${failed_logs}"
#echo "Please find the attached log file for more details"
exit 1
else
echo "`date +\"%Y-%m-%d %H:%M:%S\"` [INFO] $message [Status] $status : success" | tee -a "${success_logs}"
fi
}
`hive -e "create table testing.${table} as select * from fishing.${table}"`
cp /home/$USER/logs/"$1" /home/$USER/debug/"$1"
g_STATUS=$?
log_status $g_STATUS "Hive create ${table}"
echo "***********************************************************************************************************************************************************************"
If I have this in my shell script
exec 2>&1 | tee /home/logging/"$1"
Then I am getting logs only on console not on the redirected file.
If I have this in my script
exec> /home/logging/"$1" 2>&1
Then I am having logs on the redirected file but not on the console.
How can I have logs both on console and redirected file
You can use process substitution with exec builtin:
exec > >(tee trace.log) 2>&1
to redirect both stdout and stderr to a file as as well as show it in terminal.
The purpose of the tee command is specifically intended to direct the output to both a file and to the terminal, which is what it sounds like you're wanting. This can be replicated pretty easily with something like the following:
script.sh:
#!/usr/bin/bash
date 2>&1 | tee "$1"
Then, running the command with ./script.sh abc.txt will produce the output of the date command to the terminal as well as the file abc.txt
In your case, exec 2>&1 | tee /home/logging/"$1" should correctly produce the results you want, but you will need to call the script with that argument carefully. That assumes the /home/logging directory exists, and you call the script above with something like ./script log.txt

if command "cat /dev/net/tun" result $string then

I'm creating a script which check if a VPS do have TUN driver enabled.
The check command is :
cat /dev/net/tun
if it return:
cat: /dev/net/tun: File descriptor in bad state
the module is enabled. otherwise return ERROR.
Here is my script:
tunstring="File descriptor in bad state"
if cat /dev/net/tun | grep -q "$tunstring"; then
echo "GOOOOOD"
else
echo "ERROR"
fi
I get ERROR message.
I tried the same script with a text file and it worked...
Since that output is being written on stderr you can use:
tunstring="File descriptor in bad state"
if cat /dev/net/tun |& grep -q "$tunstring"; then
echo "GOOOOOD"
else
echo "ERROR"
fi
|& pipes previous command's stdout and stderr to next in pipe line.
Looks like your VPS path i.e /dev/net/tun isn't valid anymore and cat command is failing to read it.

Print on terminal and into file simultaneously?

I have a shell script that greps some data.. I want to print the result into a file, but doing that prevents the result being displayed on the terminal. Is there a way that can both print the result on the screen and also write into a file.
Thanks in advance.
Pipe your output to the tee command.
Example:
[me#home]$ echo hello | tee out.txt
hello
[me#home]$ cat out.txt
hello
Note that the stdout of echo is printed out as well as written to the file specified by thr tee command.
Note you can add the -a flag to tee to append to the output file
[me#home]$ echo hello | tee out.txt
hello
[me#home]$ echo hello again | tee -a out.txt
hello again
[me#home]$ cat out.txt
hello
hello again
Does exactly your thing
http://linux.die.net/man/1/tee

How do I write standard error to a file while using "tee" with a pipe?

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?

Resources