Introduction to Linux Strace Command
The Linux operating system is the go-to platform for software developers, system administrators, and IT professionals around the world. As such, mastering the command-line interface of Linux is a necessary skill for anyone who wants to work with Linux-based systems.
One of the most useful tools in the Linux command line toolkit is the strace command.
The strace command is a powerful utility that allows you to trace and debug system calls made by an executed program.
It is a useful tool when troubleshooting an application or debugging an executable that is not behaving as expected. In this article, we will explore the different functionalities of the strace command and how it can be used in a variety of scenarios.
Example of Running Basic Strace Command
The syntax for running a basic strace command is straightforward – simply prefix the command with the strace keyword. For example, running the “ls” command would look like this:
“`bash
strace ls -l
“`
This command will execute the “ls” command and print out the system calls made by the executable. The output of the command will show you the system calls being made, the arguments passed to those system calls, and the result of the system call.
Example Usages of Strace Command
1. Counting System Calls using -c Option
The strace command has an option that allows you to count the number of system calls made by the executable.
This is useful when you want to get a general idea of the system calls being made by the program.
To use the -c option, you simply prefix the strace command with the -c flag.
For example, running the “ls” command with the -c option would look like this:
“`bash
strace -c ls -l
“`
The output of the command will show you the number of calls made to each system call, as well as the total time spent in those calls.
2.
Displaying Specific System Calls using -e Option
The -e option in the strace command allows you to display only specific system calls made by the executable. This is useful when you want to monitor only specific system calls without being overwhelmed by the other system calls made by the program.
To use the -e option, you simply prefix the strace command with the -e flag followed by the system call you want to monitor. For example, running the “ls” command with the -e option to monitor only “open” system calls would look like this:
“`bash
strace -e open ls -l
“`
The output of the command will show you only the “open” system calls made by the program.
3.
Tracing Network System Calls using trace=network Option
The strace command also has an option that allows you to trace network system calls made by the executable. This is useful when you want to monitor network activity of the program.
To use the trace=network option, you simply prefix the strace command with the trace=network flag. For example, running the “wget” command with the trace=network option would look like this:
“`bash
strace -e trace=network wget https://www.example.com
“`
The output of the command will show you the network system calls made by the “wget” command, such as DNS resolution and connection establishment.
4. Tracing Signal System Calls using signal-caller Argument
The strace command can also trace signal system calls made by the program.
This is useful when you want to monitor the program response to signals. To trace signal system calls, you need to use the signal-caller argument followed by the signal name.
For example, running the “kill” command with the signal-caller argument to trace the SIGTERM signal would look like this:
“`bash
strace -e signal=SIGTERM kill
“`
The output of the command will show you the system calls made by the “kill” command when sending the SIGTERM signal to the process. 5.
Printing Timestamp of Each System Call using -r Option
The -r option in the strace command allows you to print the timestamp of each system call made by the executable. This is useful when you want to measure the time between system calls.
To use the -r option, you simply prefix the strace command with the -r flag. For example, running the “ls” command with the -r option would look like this:
“`bash
strace -r ls -l
“`
The output of the command will show you the timestamp of each system call made by the program. 6.
Printing Duration of Time Spent for Every System Call using -T Option
The -T option in the strace command allows you to print the duration of time spent for every system call made by the executable. This is useful when you want to measure how long the program takes to execute a specific system call.
To use the -T option, you simply prefix the strace command with the -T flag. For example, running the “ls” command with the -T option would look like this:
“`bash
strace -T ls -l
“`
The output of the command will show you the time taken by each system call made by the program. 7.
Displaying Exact Time of Each System Call using -t Option
The -t option in the strace command allows you to display the exact time of each system call made by the executable. This is useful when you want to measure the time the program takes to execute specific system calls.
To use the -t option, you simply prefix the strace command with the -t flag. For example, running the “ls” command with the -t option would look like this:
“`bash
strace -t ls -l
“`
The output of the command will show you the exact time of each system call made by the program. 8.
Printing Instruction Pointer for Every System Call using -i Option
The -i option in the strace command allows you to print the instruction pointer for every system call made by the executable. This is useful when you want to track the program’s execution flow at a low level.
To use the -i option, you simply prefix the strace command with the -i flag. For example, running the “ls” command with the -i option would look like this:
“`bash
strace -i ls -l
“`
The output of the command will show you the instruction pointer of each system call made by the program. 9.
Saving Output of System Calls to a Text File
The output of the strace command can be saved to a text file for further analysis. This is useful when you want to share the output with others or when you want to analyze the output at a later time.
To save the output of the strace command to a text file, you simply redirect the output to a file using the “>” operator. For example, running the “ls” command and saving the output to a text file called output.txt would look like this:
“`bash
strace ls -l > output.txt
“`
The output of the strace command will be saved to the output.txt file.
Conclusion
The strace command is a powerful utility that can be used to trace and debug system calls made by an executed program. It is a versatile tool that offers a range of functionalities that can be used in different scenarios.
By mastering the strace command, you can become a more effective Linux system administrator, software developer, or IT professional. Linux strace command is a powerful debugging tool that captures and displays system-level activities of a program.
Strace command traces all the system calls that are executed by a program and helps troubleshoot issues. In this article, we explored various commands and options that can be used with the strace command to analyze system-level activities of a program.
When running applications on Linux, there are times when you encounter problems that can be difficult to resolve. Fortunately, with the Linux strace command, you can easily identify the root cause of the problem by monitoring the system calls made by the program.
It is an indispensable tool for troubleshooting and debugging programs. Here are some ways you can use the Linux strace command to monitor programs and address issues.
Counting System Calls using the -c Option
The strace -c command prints a summary of the numbers and times for each system call performed by the program. This option is very useful for identifying which system calls the program uses most and how much time it spends doing so.
For example, running the command “
strace -c ls -l”, shows the number of syscalls made by the ls command and their distribution.
Displaying Specific System Calls using the -e Option
The -e option is used to specify the system calls to be monitored. By using this option, you can monitor specific system calls and ignore others.
For example, running the command “
strace -e open ls -l” shows that only open system calls are made and their distribution. Tracing Network System Calls using the trace=network Option
The strace command can trace system calls related to network activities.
This is useful when you want to monitor network activity of a program. The strace -e trace=network command can trace network-related system calls and display the details of each network call.
For example, running the command “strace -e trace=network wget https://www.example.com” displays network system calls made by the wget command such as DNS resolution and connection establishment.
Tracing Signal System Calls using the signal-caller Argument
Signal system calls are responsible for handling signals caused by user actions or system events. If your program has issues with signal handling, it can cause problems for the program.
The strace command can trace signal system calls to help you diagnose signal handling problems. You can use the strace -e signal=SIGTERM command to track the SIGTERM signal sent to a process.
For example, running the command “strace -e signal=SIGTERM kill
Printing Timestamp of Each System Call using the -r Option
The -r option in the strace command prints the timestamp for each system call made by the program. This helps you measure the time interval between system calls.
For example, running the command “
strace -r ls -l” displays the timestamp of each system call.
Printing Duration of Time Spent for Every System Call using the -T Option
The -T option in the strace command prints the duration of time spent by each system call. It helps you to identify which system calls take the most time.
For example, running the command “
strace -T ls -l” shows the time taken by each system call made by the program.
Displaying Exact Time of Each System Call using the -t Option
The -t option in the strace command displays the exact time of each system call made by the program. It provides more detailed information compared to the -r option.
For example, running the command “
strace -t ls -l” displays the exact time of each system call made by the program.
Printing Instruction Pointer for Every System Call using the -i Option
The -i option in the strace command prints the instruction pointer for every system call made by the program. It helps you track the execution flow of the program at a low level.
For example, running the command “
strace -i ls -l” displays the instruction pointers of each system call made by the program.
Saving Output of System Calls to a Text File
The output of the strace command can be saved to a text file for further analysis. You can use the “>” operator to redirect output to a file.
For example, running the command “
strace ls -l > output.txt” saves the output of the strace command to the output.txt file. In conclusion, the strace command is an indispensable tool for troubleshooting and debugging programs on Linux.
It provides insights into the inner workings of a program by capturing system-level activities. The different strace options and commands can be used to monitor specific system calls, trace network calls, identify performance issues, and record output for further analysis.
By mastering the strace command, you can become a more effective Linux system administrator, software developer, or IT professional. In conclusion, the Linux strace command is an essential tool for debugging and troubleshooting programs on a Linux operating system.
By tracing system calls, it enables users to identify issues and understand the behavior of programs at the system level. Through the examples explored in this article, we have seen how the strace command can be used to count system calls, display specific calls, trace network and signal calls, print timestamps and durations, and save output to a file.
Mastering the strace command empowers Linux users to diagnose problems more effectively and optimize program performance. With its ability to uncover system-level activity, the strace command is an invaluable asset for system administrators, developers, and IT professionals.
Armed with this knowledge, you can confidently tackle complex issues and gain deeper insights into the inner workings of your Linux-based applications.