used to detect as many problems as a code debugger such as GNU Debugger (gdb). It is, however, easier to use than a code debugger, and is a very useful tool for system administrators. It is also used by researchers to generate system call traces for later system call replay. Examples The following is an example of typical output of the strace command: user@server:~$ strace ls ... open(".", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = 3 fstat64(3, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 fcntl64(3, F_GETFD) = 0x1 (flags FD_CLOEXEC) getdents64(3, /* 18 entries */, 4096) = 496 getdents64(3, /* 0 entries */, 4096) = 0 close(3) = 0 fstat64(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f2c000 write(1, "autofs\nbackups\ncache\nflexlm\ngames"..., 86autofsA The above fragment is only a small part of the output of strace when run on the 'ls' command. It shows that the current working directory is opened, inspected and its contents retrieved. The resulting list of file names is written to standard output. Similar tools Different operating systems feature other similar or related instrumentation tools, offering similar or more advanced features; some of the tools (although using the same or a similar name) may use completely different work mechanisms, resulting in different feature sets or results. Such tools include the following: Linux has ltrace that can trace library and system calls, xtrace that can trace X Window programs, SystemTap, perf, and trace-cmd and KernelShark that extend ftrace. AIX provides the command HP-UX offers the command Solaris / Illumos has truss and DTrace UnixWare provides the command FreeBSD provides the command, ktrace and DTrace NetBSD provides ktrace and DTrace OpenBSD uses ktrace and kdump macOS provides ktrace (10.4 and earlier), DTrace (from Solaris) and associated dtruss in 10.5 and later. Microsoft Windows has a similar utility called StraceNT, written by Pankaj Garg, and a similar GUI-based utility called Process Monitor, developed by Sysinternals. See also gdb List of Unix commands lsof Notes References External links strace project page Manual page OS Reviews article on strace "System Call Tracing with strace", a talk with an overview of strace features and usage, given by Michael Kerrisk at NDC TechTown 2018 "Modern strace" (source), a talk with an overview of strace features, given by Dmitry Levin at DevConf.cz 2019 Unix programming tools Command-line software Free software programmed in C