strace Command: Tutorial & Examples
strace is a system call tracer, meaning it can be used to monitor the system calls and signals of a specific
program. It's a great tool for debugging and understanding what's happening under the hood.
What it does
strace intercepts and records the system calls made by a process. It also captures the signals received by the
process. This can be particularly useful when you're trying to troubleshoot a misbehaving program.
How it works
strace works by utilizing the
ptrace system call to hook into the target process. Once
hooked, it can monitor the system calls made by the process and the signals it receives.
What it is used for
strace is widely used for debugging and troubleshooting purposes. It allows a user to see what system calls a program
is making. This can be useful in a variety of scenarios:
- Finding out why a program is failing to run or behaving unexpectedly.
- Understanding how a program interacts with the system.
- Troubleshooting a performance problem.
Why it is important
Understanding the system calls a program makes can shed light on its inner workings. For example, if a program is
strace can help identify if the program is making unnecessary system calls, waiting on I/O, or if
there's a network issue. This makes it a vital tool for anyone maintaining or
troubleshooting Linux servers.
How to use it
The basic usage of
strace is quite simple. Just prepend the command you want to trace with
strace. For example, to
ls command, you would run:
This will print out a list of all system calls made by the
Some common options you might use with
-c: This option counts the number of times each system call is made and provides a summary.
-f: This option traces child processes as they are created by currently traced processes.
-p: This option attaches
straceto a running process with a specific PID.
For example, to attach
strace to a running process with a PID of 1234, you would run:
strace -p 1234
Potential problems and pitfalls
strace is a powerful tool, it's not without its quirks. Here are a few things to keep in mind:
stracecan add a significant amount of overhead. This can slow down the program you're trying to debug.
- Noise: The output of
stracecan be overwhelming, especially for programs that make a lot of system calls.
- Interpretation: Interpreting the output of
stracecan be challenging unless you're familiar with the system calls being made.