Tail Container Logs In Docker

The short answer

In Docker, retrieving the logs of containers during their execution allows to simplify the debugging and tracing issues for developers.

To output the logs of a specific Docker container, you can use the docker logs command as follows:

 $ docker logs <container_id>

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Where container_id is either the name or the identifier of the container, which can be obtained using the docker ps command.

For example, this command will output the logs of the container named container_zero:

 $ docker logs container_zero

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And this command will output the logs of the container with the ID 7783cbb0deaa:

 $ docker logs 7783cbb0deaa

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Displaying container logs in real-time

To monitor the logs of a docker container in real-time, you can use the docker logs command with the -f flag (short for --follow):

 $ docker logs -f <container_id>

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For example:

 $ docker logs -f 5228d692b669

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Easily retrieve this command using Warp’s AI Command Suggestions

If you’re using Warp as your terminal, you can easily retrieve this command using the Warp AI Command Suggestions feature:

Entering docker logs real-time in the AI Command Suggestions will prompt a docker command that can then quickly be inserted into your shell by doing CMD+ENTER.

Filtering container logs

In Docker, container logs can be filtered in several ways.

Outputting the last N logs

To show the latest log entries, you can use the --tail option, followed by the number of logs to display:

 $ docker logs --tail <number> <container_id>

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For example, the following command shows the latest 80 logs of the container identified by the ID 5228d692b669:

 $ docker logs --tail 80 5228d692b669

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Filtering logs by date and time

To filter container logs based on timeframes, you can either use the --since flag to fetch the logs that occurred after a specific time:

 $ docker logs --since <time> <container_id>

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Or you can use the --until flag to fetch the logs that occurred before a specific:

 $ docker logs --until <time> <container_id>

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Where time is either:

• A timestamp expressed in the following format: YYYY-MM-DDTHH:MM:SS.NNNNNNZ.
• A relative duration expressed in the following format: <number>[h|m|s] where h, m, s stand for hours, minutes, and seconds.

For example, this command will output the logs generated in the last hour:

 $ docker logs --since="1h" 5228d692b669

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And this command will output the logs generated until January 2nd, 2024:

 $ docker logs --until="2024-01-02"  5228d692b669

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Filtering logs based on patterns using the grep command

To filter the container logs based on specific keywords or patterns, you can pipe the output of the docker logs command into the grep command:

 $ docker logs <container_id> | grep '<pattern>'

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For instance, if the container is throwing an error, you can find out more about it by searching for the ERROR keyword:

 $ docker logs 5228d692b669 | grep 'ERROR'

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