System information

Tracing Tools 195
The -e option understands several sub-options and arguments. For example, to trace
all attempts to open or write to a particular file, use the following:
tux@mercury:~> strace -e trace=open,write ls ~
open("/etc/ld.so.cache", O_RDONLY) = 3
open("/lib64/librt.so.1", O_RDONLY) = 3
open("/lib64/libselinux.so.1", O_RDONLY) = 3
open("/lib64/libacl.so.1", O_RDONLY) = 3
open("/lib64/libc.so.6", O_RDONLY) = 3
open("/lib64/libpthread.so.0", O_RDONLY) = 3
[...]
open("/usr/lib/locale/cs_CZ.utf8/LC_CTYPE", O_RDONLY) = 3
open(".", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
write(1, "addressbook.db.bak\nbin\ncxoffice\n"..., 311) = 311
To trace only network related system calls, use -e trace=network:
tux@mercury:~> strace -e trace=network -p 26520
Process 26520 attached - interrupt to quit
socket(PF_NETLINK, SOCK_RAW, 0) = 50
bind(50, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
getsockname(50, {sa_family=AF_NETLINK, pid=26520, groups=00000000}, \
[12]) = 0
sendto(50, "\24\0\0\0\26\0\1\3~p\315K\0\0\0\0\0\0\0\0", 20, 0,
{sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 20
[...]
The -c calculates the time the kernel spent on each system call:
tux@mercury:~> strace -c find /etc -name xorg.conf
/etc/X11/xorg.conf
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
32.38 0.000181 181 1 execve
22.00 0.000123 0 576 getdents64
19.50 0.000109 0 917 31 open
19.14 0.000107 0 888 close
4.11 0.000023 2 10 mprotect
0.00 0.000000 0 1 write
[...]
0.00 0.000000 0 1 getrlimit
0.00 0.000000 0 1 arch_prctl
0.00 0.000000 0 3 1 futex
0.00 0.000000 0 1 set_tid_address
0.00 0.000000 0 4 fadvise64
0.00 0.000000 0 1 set_robust_list
------ ----------- ----------- --------- --------- ----------------
100.00 0.000559 3633 33 total
To trace all child processes of a process, use -f:
tux@mercury:~> strace -f rcapache2 status
execve("/usr/sbin/rcapache2", ["rcapache2", "status"], [/* 81 vars */]) = 0