YouTipLinux ltrace Command |
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ltrace is a utility in Linux systems used to track and record dynamic library functions called during program execution. It is a powerful tool for debugging and analyzing program behavior, especially suitable for the following scenarios:
- View which library functions the program calls
- Understand the parameters and return values of function calls
- Diagnose interaction issues between the program and library functions
- Analyze program performance bottlenecks
Unlike the strace command (which tracks system calls), ltrace focuses on user-space library function calls.
Install ltrace
Most Linux distributions do not have ltrace installed by default. You can install it using the package manager:
Examples
Debian/Ubuntu
sudo apt-get install ltrace
CentOS/RHEL
sudo yum install ltrace
Fedora
sudo dnf install ltrace
Arch Linux
sudo pacman -S ltrace
Basic Syntax
The basic command format for ltrace is:
ltrace program_to_trace
Or attach to a running process:
ltrace -p PID
Common Options
| Option | Description |
|---|---|
-c | Count function calls and time, output summary at the end |
-e | Only trace specified functions (supports wildcards) |
-f | Trace child processes |
-i | Print instruction pointer (IP) |
-l | Only trace functions from specified library |
-n | Specify indentation level for output lines |
-o | Write output to file |
-p | Attach to running process |
-r | Print relative timestamp |
-S | Also trace system calls |
-t | Add time prefix to each line |
-T | Show time spent in each call |
-u | Run as specified user |
Usage Examples
Basic Tracing Example
Trace library function calls of a simple program:
ltrace ./my_program
Example output:
printf("Hello, World!n") = 13
malloc(1024) = 0x55a1a2e2e260
free(0x55a1a2e2e260) =
Count Function Calls
Use the -c option to get statistics on function calls:
ltrace -c ./my_program
Example output:
% time seconds usecs/call calls function
------ ----------- ----------- --------- --------------------
45.23 0.123456 123 1000 malloc
32.12 0.087654 87 1000 free
22.65 0.061728 61 1000 printf
Trace Specific Functions
Only trace malloc and free functions:
ltrace -e "malloc,free" ./my_program
Attach to Running Process
Trace process with PID 1234:
ltrace -p 1234
Show Call Duration
Use the -T option to show time spent in each call:
ltrace -T ./my_program
Example output:
malloc(1024) = 0x55a1a2e2e260 <0.000123>
free(0x55a1a2e2e260) = <0.000045>
Practical Application Cases
Case 1: Analyze Memory Allocation
ltrace -e "malloc,free" ./memory_intensive_program
Through this command, you