Retrieve Logs from Multiple Containers on Remote Server

Question

Recently I had the requirement to allow multiple containers of the same application to be run on a single development server. This requirement drastically changed how we retrieve logs over SSH from the servers, and because I am not extremely well versed in bash, I wanted to get this script reviewed to see if there is an easier/cleaner way to approach this problem.

The goal of the script is to produce a single log file on the local system for each container on that is running on the remote server. It is currently working as expected for 1 and N containers running on a single server.

The script I wrote does the following:

1. Verify that the server being requested can provide the logs
2. SSH into the remote server and save the logs for each container to a file on the local system
3. Post-Process the logs into individual log files for each container that is present

I am fairly certain there is a much easier way to accomplish this task, hence the post here to see if anyone can point me in the right direction (I have a feeling, as I write this, that I can just scp the docker log files for each container to the local system instead of all of this.... But I also want to practice some bash, so I would still like this reviewed)

Script:

#!/bin/bash
# Add a help parameter to the script
if [ "1ドル" == "-h" ] || [ "1ドル" == "-help" ]; then
 echo "Usage: $(basename "0ドル")"
 echo " Logs will be placed in /c/temp/logs/<server>.log"
 echo " Prompts:"
 echo " - Username: AD Username for Logins"
 echo " - Server: This is a dev server, valid choices are:"
 echo " (<SERVER_NAME>1 <SERVER_NAME>2 <SERVER_NAME>3 <SERVER_NAME>4)"
 exit 0
fi
# Create an array of valid servers to check for logs
servers=(<SERVER_NAME>1 <SERVER_NAME>2 <SERVER_NAME>3 <SERVER_NAME>4)
# Ask the user where they want to get the logs from
read -rp "Username: " user
read -rp "Server: " server
# Validate the server can retrieve logs
foundServer=0
for i in "${servers[@]}"; do
 if [ "$i" == "$server" ]; then
 foundServer=1
 break
 fi
done
if [ $foundServer == 0 ]; then
 echo "Please select a dev server"
 echo "Use -h or -help for help with $(basename "0ドル")"
 exit 1
fi
# Set the working directory
(cd /c/temp/logs/temp/ &&
 # Get the logs. Servers with multiple containers will have the following structure:
 # HeaderA
 # A
 # A
 # A
 # HeaderB
 # B
 # B
 # B
 now=$(date '+%Y%m%d_%H%M')
 ssh -tt "$user"@"$server" "sudo setfacl --modify user:${user}:rw /var/run/docker.sock && docker ps --format '{{.Names}}' | xargs -L 1 -t docker logs" > ./"${server}_${now}.log"
 # Process the temp file into individual files for each container ....
 # Get the headers for each Log File
 grep -n "docker logs" ./"${server}_${now}.log" >> ./docker_logs.txt
 total_matches=$(wc -l ./docker_logs.txt | cut -d' ' -f1)
 # From Line 1 -> First Match == Log A, From First Match -> Next Match == Log B, etc
 start_line=1
 # Get the file name for the first file
 file_name_match=$(head -n 1 ./docker_logs.txt)
 current_name=$(echo "$file_name_match" | cut -f2 -d: | sed "s/^docker logs //")
 # Get the end line index for the first file
 end_line_text=$(awk "NR==2" ./docker_logs.txt | cut -f1 -d:)
 if [[ $end_line_text ]]; then
 end_line=$(("$end_line_text"-1))
 else
 end_line="$"
 fi
 # Skipping the first file (starting from index 2), loop through any log files that are present
 for (( n=2; n<="$total_matches"+1; n++ )) do
 # Copy the current file from start -> end to the log file for the current name, if end_line was EOF
 # then break from the loop
 sed -n "${start_line},${end_line}p" ./"${server}_${now}.log" > ../"${server}_${now}_${current_name}.log"
 if [[ $end_line == "$" ]]; then
 break
 fi
 # Get the start line of the next file
 start_line=$(("$end_line"+1))
 # Get the file name of the next log file
 file_name_match=$(awk "NR==$n" ./docker_logs.txt)
 current_name=$(echo "$file_name_match" | cut -f2 -d: | sed "s/^docker logs //")
 # Get the ending index of the next log file, if there is nothing returned, set end_line to
 # be the EOF
 end_index=$(("$n"+1))
 end_line_text=$(awk "NR==$end_index" ./docker_logs.txt | cut -f1 -d:)
 if [[ $end_line_text ]]; then
 end_line=$(("$end_line_text"-1))
 else
 end_line="$"
 fi
 done
 # Remove the temp files
 rm -f /c/temp/logs/temp/*
)
# Open the logs directory for the user
start /c/temp/logs/

This produces N number of logfiles on the local system, of the format ${server}_${now}_${container_name}.log.

Answer 1

Error messages should be redirected to stream 2 (standard error):

if [ "$foundServer" == 0 ]
then
 echo >&2 "Please select a dev server"
 echo >&2 "Use -h or -help for help with $(basename "0ドル")"
 exit 1
fi

Or,

if [ "$foundServer" == 0 ]
then
 exec >&2
 echo "Please select a dev server"
 echo "Use -h or -help for help with $(basename "0ドル")"
 exit 1
fi

Answer 2

good

• Good shbang line. (Consider env for PATH portability.)
• Good variable names.
• Good indentation.
• Good comments

suggestions

• I'm assuming you're replacing <SERVER_NAME> with some value in practice. If that is true, you might consider making that a variable so you can use this for other kinds of servers.
• Using the subshell to let you change directories and get back to where you started is interesting, but unless you're getting some other non-obvious benefit from the subshell I'd use pushd /c/temp/logs/temp/ to get into the directory and popd to get out of it.
• Double square brackets for shell conditionals have fewer surprises.
• When doing shell math such as $(("$n"+1)) you don't need the quotes or the dollar sign. The double parens tell it to evaluate mathematically and that gets you variables too. So $((n+1)) will work just as well and is easier to read.

• Toby Speight: I disagree on pushd and popd. They are much better suited for interactive use, and a nuisance in scripts. They also produce output that would need to be redirected away.
• chicks: They are also good for interactive use. Using a subshell still seems like the wrong choice. You could also store $PWD in another variable like $OLDPWD and cd back to that.