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authorDenis Vlasenko2007-06-23 14:56:43 +0000
committerDenis Vlasenko2007-06-23 14:56:43 +0000
commit198badafd82905c9a2e76eeacb7ce463d8518bda (patch)
treefcb367654b5c6cafdca09ef189342fc7019095fc /libbb/find_pid_by_name.c
parent118b81df76be0e372309d76196c8eedf19ac56cd (diff)
downloadbusybox-198badafd82905c9a2e76eeacb7ce463d8518bda.zip
busybox-198badafd82905c9a2e76eeacb7ce463d8518bda.tar.gz
pidof: size optimizations (-50 bytes)
Diffstat (limited to 'libbb/find_pid_by_name.c')
-rw-r--r--libbb/find_pid_by_name.c29
1 files changed, 29 insertions, 0 deletions
diff --git a/libbb/find_pid_by_name.c b/libbb/find_pid_by_name.c
index e986169..13ccb54 100644
--- a/libbb/find_pid_by_name.c
+++ b/libbb/find_pid_by_name.c
@@ -9,6 +9,35 @@
#include "libbb.h"
+/*
+In Linux we have three ways to determine "process name":
+1. /proc/PID/stat has "...(name)...", among other things. It's so-called "comm" field.
+2. /proc/PID/cmdline's first NUL-terminated string. It's argv[0] from exec syscall.
+3. /proc/PID/exe symlink. Points to the running executable file.
+
+kernel threads:
+ comm: thread name
+ cmdline: empty
+ exe: <readlink fails>
+
+executable
+ comm: first 15 chars of base name
+ (if executable is a symlink, then first 15 chars of symlink name are used)
+ cmdline: argv[0] from exec syscall
+ exe: points to executable (resolves symlink, unlike comm)
+
+script (an executable with #!/path/to/interpreter):
+ comm: first 15 chars of script's base name (symlinks are not resolved)
+ cmdline: /path/to/interpreter (symlinks are not resolved)
+ (script name is in argv[1], args are pushed into argv[2] etc)
+ exe: points to interpreter's executable (symlinks are resolved)
+
+If FEATURE_PREFER_APPLETS=y (and more so if FEATURE_SH_STANDALONE=y),
+some commands started from busybox shell, xargs or find are started by
+execXXX("/proc/self/exe", applet_name, params....)
+and therefore comm field contains "exe".
+*/
+
/* find_pid_by_name()
*
* Modified by Vladimir Oleynik for use with libbb/procps.c