Crontab Logs Missing Dates? 4 Practical Ways to Easily Add Timestamps

## The Problem When using Crontab to execute scheduled tasks, a common issue is that the output redirected to a log file does not contain execution timestamps. This makes it difficult to trace when a specific task ran, complicating debugging and monitoring. For example, here's a typical Crontab command: ```bash 0 2 * * * docker exec my-app-container php /var/www/wiki.lib00/index.php /task/run >> /var/log/lib00/task.log 2>&1 ``` The output of this command is appended directly to `task.log`, but the log entries themselves lack timestamps. --- ## The Solutions To solve this, we can use several methods to add timestamps to our logs. Here are four practical solutions compiled by DP@lib00. ### Method 1: Add a Uniform Timestamp for Each Run (Recommended) This is the most common and recommended method. By wrapping the main command and a `date` command in curly braces `{}`, we can prepend a clear timestamp to the beginning of the task's output. This helps to separate the log blocks for each execution. ```bash # Format # 0 2 * * * { echo "=== $(date '+\%Y-\%m-\%d \%H:\%M:\%S') ==="; your_command; } >> /path/to/logfile.log 2>&1 # Example 0 2 * * * { echo "=== $(date '+\%Y-\%m-\%d \%H:\%M:\%S') ==="; docker exec my-app-container php /var/www/wiki.lib00/index.php /task/run; } >> /var/log/lib00/task.log 2>&1 ``` **Key Point**: In a crontab file, the percent sign `%` has a special meaning and must be escaped with a backslash `\`, resulting in `\%`. ### Method 2: Include the Date in the Log Filename This method is ideal if your goal is to create a new log file for each day. It uses the `date` command to dynamically generate a filename that includes the current date, effectively implementing log rotation. ```bash # Format # 0 2 * * * your_command >> /path/to/logfile_$(date +\%Y\%m\%d).log 2>&1 # Example 0 2 * * * docker exec my-app-container php /var/www/wiki.lib00/index.php /task/run >> /var/log/lib00/task_$(date +\%Y\%m\%d).log 2>&1 ``` The drawback is that if the task runs multiple times a day, all output will still be in the same file, and you won't be able to distinguish the specific execution time within the file. ### Method 3: Timestamp Every Line with the `ts` Command For scenarios requiring per-line timestamps (e.g., for long-running scripts), the `ts` command is an excellent choice. `ts` is part of the `moreutils` package, which you'll need to install first. ```bash # Debian/Ubuntu sudo apt-get install moreutils # CentOS/RHEL sudo yum install moreutils ``` Once installed, use it in your crontab like this: ```bash # Format # 0 2 * * * your_command 2>&1 | ts '\%Y-\%m-\%d \%H:\%M:\%S' >> /path/to/logfile.log # Example 0 2 * * * docker exec my-app-container php /var/www/wiki.lib00/index.php /task/run 2>&1 | ts '\%Y-\%m-\%d \%H:\%M:\%S' >> /var/log/lib00/task.log ``` This will prepend a timestamp to every line of standard output and standard error from your script. ### Method 4: Log Both Start and End Times This is an extension of Method 1. By printing the time both before and after the command execution, you can easily monitor the task's duration, which is very useful for performance analysis and troubleshooting. ```bash # Example 0 2 * * * { echo "Task Started: $(date '+\%Y-\%m-\%d \%H:\%M:\%S')"; docker exec my-app-container php /var/www/wiki.lib00/index.php /task/run; echo "Task Finished: $(date '+\%Y-\%m-\%d \%H:\%M:\%S')"; echo "---"; } >> /var/log/lib00/task.log 2>&1 ``` --- ## Conclusion Adding timestamps to Crontab logs is a crucial practice for ensuring system maintainability. For projects at wiki.lib00.com, we recommend the following: - **Method 1** and **Method 4** as general-purpose solutions. They clearly mark each task run and are easy to implement. - **Method 2** is suitable for scenarios where logs need to be split by day. - **Method 3** is the best choice when you need granular monitoring for long-running tasks. Choose the method that best fits your needs to make your Crontab logs more professional and readable.