Redis Client (Bash)

This project consists of

1. redis.bash - a Bash library for Redis containing some useful shell-functions
2. redis-cli - an executable Bash script implementing an interactive Redis console
3. redis-pool - a connection pool for Redis

Table of Contents

• Redis Client (Bash)
• Library usage
  • Low level tasks
  • Demo / Example
• CLI console
• Connection pool
• Alternative(s)
• Feedback, feature requests, bug report
• Contribution
• Support / Sponsor
• Acknowledgements
• License

Library usage

1. To use the library functions in your Bash script, source the library first: source <path to redis.bash>

2. Then, create a session using

   redis_connect [-h host] [-p port] [-a passwd] [-d database] [-t timeout in seconds]

   Instead of using options, the host, port, password, database and timeout can also be provided using the respective environment variables: REDIS_HOST, REDIS_PORT, REDIS_AUTH, REDIS_DB, REDIS_TIMEOUT. The timeout is the interval used by the automatic keepalive service. If keepalive is not required, specify a 0s timeout. The defaults are - Host: localhost ; Port: 6379 ; DB: 0 ; Timeout: 300s.

3. To execute a single Redis command in the server, and get its corresponding response, run:

   redis_exec <commmand>
   
   # Example: redis_exec 'keys *'

   This sends the command to the server and then prints the server response to stderr or stdout, depending on whether the server response data-type (RESP) is "Error" or not. The rather trivial OK and PONG responses are not printed for redirected stdout, for developer convenience. redis_exec returns after reading exactly one complete RESP response from the server. The read has a 1 second timeout. If reading from or sending the command to the server fails, redis_exec assumes that the server got disconnected and tries to reconnect and resend the command automatically.

   Note: If you forget to do redis_connect (step 1 above), then redis_exec will exit with error: Failed to acquire lock 1. In that case, simply do step 1 and then retry redis_exec.

4. To end session with the server, simply do: redis_disconnect

Low level tasks

redis_read [-t <timeout>]: for parsing RESP

redis_rep [-t <timeout>] [-n N]: for reading N complete RESP responses and printing the values at stdout or stderr based on the RESP data-type(s); N=0 implies an infinite reading loop useful for reading push messages.

See documentation in redis.bash for details.

Demo / Example

Checkout the code in redis-cli . It uses the client-library only.

CLI console

./redis-cli -h <host> -p <port> -a <passwd> -t <idle timeout s> -d <database no.>

To quit, enter any of the following: q , exit , quit (case-insensitive)

Note: If subscribed to push messages with (P)SUBSCRIBE channel or MONITOR, simply do Ctrl-C (i.e. ^C) followed by Enter to return to the normal interactive mode, i.e. get the command prompt back.

Connection pool

redis-pool offers simple connection pooling with support for both Unix domain and TCP sockets. The local socket serves as a proxy for the remote Redis server. If the number of concurrent connections/requests to this proxy is more than what the server can support, the excess requests will be put on hold (i.e. blocking) and served whenever a spot opens up.

Following are simple examples using Unix domain sockets. For using TCP ports instead, simply replace path/socket with the port number and remove the -U flag in nc:

1. In one terminal :

   ./redis-pool -n <max connections> -h <host> -p <port> -a <pass> path/socket

2. In another terminal:

   . redis.bash # In order to define redis_rep
   
   # Pipelining 2 commands in one go
   echo -e "set foo bar\nget foo" | nc -N -U path/socket | redis_rep -n 2
   
   # Activating the push protocol: pub-sub
   echo "subscribe channel" | nc -U path/socket | redis_rep -n 0

3. In still another terminal:

   ./redis-cli
   localhost:port_db$ publish channel hello
   # Check now if you got the message in the second terminal

Note: We use echo with the Redis commands instead of printf or echo -n. The pool transforms trailing LF to CRLF before sending each inline command to the server.

Alternative(s)

https://redis.io/clients#bash

https://github.com/caquino/redis-bash

Feedback, feature requests, bug report

Create an issue at the project repository or write to me.

If you like this project, please consider giving it a star at GitHub to encourage me.

Contribution

PRs are welcome. Please follow this minimal style guide when contributing:

• No camelCase. Only under_scores.
• Do, If, Case and For constructs as in redis.bash

Also put your name and email id in the comments section of your code-block.

If you cannot submit a PR at GitHub, feel free to send me your patch over email. Just mention the Git commit hash in the project repository to which the patch should be applied.

Open issue: Making the docs better.

Support / Sponsor

Acknowledgements

TY: @zuiderkwast

License

GNU Lesser General Public License - 2.1

Copyright (C) Somajit Dey, 2021