I have tried the below two options in crontab and expecting to get only stderr in the log file. However, some non-error lines related to mongodump command in the script file appear in the log file. I have seen various posts on stderr piping here, but couldn’t get what I wanted. Where am I going wrong?

The two crontab options that are tried:

0 0 * * * /root/scripts/dev-vps_backup.sh >> logfile.log 2>&1 > /dev/null

0 0 * * * /root/scripts/dev-vps_backup.sh 2>&1 >> all.log | tee -a all.log err.log >&2

the bash script file:

#!/bin/bash

set -e

#start time var
start_time=$(TZ=Asia/Calcutta date +%d-%m-%Y_%H-%M-%S)
echo "Started Script: " $(basename "$0") "@ $start_time"

#########UPDATE THIS###########
### setting up variables here
######################## END of UPDATE

#create backup folders
mkdir -p $local_backupfolder
mkdir -p $local_dumps_backupfolder
mkdir -p $local_assets_backupfolder

# remote backup storage
remote_base_backupfolder=root@$remote_IP:/root/r-backups/$vps_name


# mongodump
gzfile=$local_dumps_backupfolder/$vps_name--dump--$start_time.gz
dumpMsg="$vps_name mongodump StartTime:$start_time, EndTime:"

if mongodump --gzip --archive=$gzfile ; then   ### THIS generates lines that are shown in stderr file
  echo "DONE: $dumpMsg $(TZ=Asia/Calcutta date +%d-%m-%Y_%H-%M-%S)"
else
  echo "ERR: $dumpMsg $(TZ=Asia/Calcutta date +%d-%m-%Y_%H-%M-%S)" | mailx -s "ERR: $vps_name mongodump" $recipient_email
  exit
fi

zipMsg1="$vps_name - $app_name1 - ZIP file for folder: $local_assets_folder1. StartTime:$start_time, EndTime:"

if zip -r $local_assets_backupfolder/$vps_name--$app_name1--assets-$(TZ=Asia/Calcutta date +%d-%m-%Y_%H-%M-%S).zip $local_assets_folder1 ; then
   echo "DONE: $zipMsg1 $(TZ=Asia/Calcutta date +%d-%m-%Y_%H-%M-%S)"
else
   echo "ERR: $zipMsg1 $(TZ=Asia/Calcutta date +%d-%m-%Y_%H-%M-%S)" | mailx -s "ERR: $vps_name - $app_name1 - assets local ZIP" $recipient_email
   exit
fi

some1-some_command  # to generate error

## some more lines

err.log file:

2024-08-02T10:33:01.116+0200    writing admin.system.version to archive '/root/backups/dumps/fvc1-vps--dump--02-08-2024_14-03-01.gz'
2024-08-02T10:33:01.118+0200    done dumping admin.system.version (1 document)
2024-08-02T10:33:01.118+0200    writing myca.syslogs to archive '/root/backups/dumps/fvc1-vps--dump--02-08-2024_14-03-01.gz'
.....some more lines related to mongodump command....
/root/scripts/fvc1-vps_backup.sh: line 61: some1-some_command: command not found

all.log file has the additional lines related to echo command and zip command.

EXPECTED: Only the last line in err.log file – which is the error. How do I achieve this?

UPDATE

tried this crontab:

59 11 * * * /root/scripts/fvc1-vps_backup.sh >> /root/scripts/logfile.log

resultant logfile:

Started Script:  fvc1-vps_backup.sh @ 02-08-2024_15-29-01
DONE: fvc1-vps mongodump StartTime:02-08-2024_15-29-01, EndTime: 02-08-2024_15-29-01
  adding: root/jobs/assets/ (stored 0%)
  adding: root/jobs/assets/tempfiles/ (stored 0%)
        ...... some more lines resulting from zip command.....
  adding: root/jobs/assets/invoiceDocs/ (stored 0%)
DONE: fvc1-vps - jobs - ZIP file for folder: /root/jobs/assets. StartTime:02-08-2024_15-29-01, EndTime: 02-08-2024_15-29-19

The log file doesnot include mongodump related lines. That means these lines are going to stderr (as show in the first log file result). Not sure why?