Developing and managing software on Linux can be challenging, especially when encountering unexpected behavior or performance issues. strace is a tool that allows you to peek under the hood of your application by tracing the system calls between the application and the operating system kernel. In this article, we will explore how to use strace for analysis and diagnostics of applications on CentOS 7.
Installing strace on CentOS 7
Before you can use strace, you need to ensure it is installed on your system. On CentOS 7, you can install strace using the yum package manager. Open a terminal and run the following command:
sudo yum install strace
Basic Usage of strace
After installation, you can run strace to analyze any running process. The basic syntax of the command is:
strace [options] [command]
To run strace on an already running process, use the -p option followed by the process ID (PID):
strace -p PID
If you want to trace how an application spawns new processes, you can add the -f option, which traces all child processes spawned by the original process.
Analyzing the Output
The output of strace may initially seem cryptic, but it provides valuable insights into how an application interacts with the operating system. Each line of output typically represents a single system call along with its arguments and return value. For example:
open("/etc/hosts", O_RDONLY) = 3
This line indicates that the application attempted to open the file /etc/hosts for reading only (O_RDONLY), and the operation succeeded with a return value of 3, which is the file descriptor for the opened file.
Using for Performance Issue Diagnosis
strace can also be useful for diagnosing performance issues. The -c option displays a summary of system call statistics after the trace is completed. This can help identify which calls are most frequent or where delays may occur.
strace -c -p PID
strace is a powerful tool for developers and system administrators, providing deeper insight into application behavior on the system. Its ability to trace system calls in real-time and provide detailed information on interactions between applications and the operating system kernel is invaluable for diagnostics and issue resolution. With practice and patience, strace becomes an essential tool in your developer or administrator toolkit.
