How do I find the process ID of a program with a particular name
In a shell script:
There is no utility specifically designed to map between program
names and process IDs. Furthermore, such mappings are often
unreliable, since it's possible for more than one process to have
the same name, and since it's possible for a process to change
its name once it starts running. However, a pipeline like this
can often be used to get a list of processes (owned by you) with
a particular name:
ps ux | awk '/name/ && !/awk/ {print $2}'
You replace "name" with the name of the process for which you are
searching.
The general idea is to parse the output of ps, using awk or grep
or other utilities, to search for the lines with the specified
name on them, and print the PID's for those lines. Note that the
"!/awk/" above prevents the awk process for being listed.
You may have to change the arguments to ps, depending on what
kind of Unix you are using.
In a C program:
Just as there is no utility specifically designed to map between
program names and process IDs, there are no (portable) C library
functions to do it either.
However, some vendors provide functions for reading Kernel
memory; for example, Sun provides the "kvm_" functions, and Data
General provides the "dg_" functions. It may be possible for any
user to use these, or they may only be useable by the super-user
(or a user in group "kmem") if read-access to kernel memory on
your system is restricted. Furthermore, these functions are
often not documented or documented badly, and might change from
release to release.
Some vendors provide a "/proc" filesystem, which appears as a
directory with a bunch of filenames in it. Each filename is a
number, corresponding to a process ID, and you can open the file
and read it to get information about the process. Once again,
access to this may be restricted, and the interface to it may
change from system to system.
If you can't use vendor-specific library functions, and you
don't have /proc, and you still want to do this completely
in C, you
are going to have to do the rummaging through kernel memory
yourself. For a good example of how to do this on many systems,
see the sources to "ofiles", available in the comp.sources.unix
archives. (A package named "kstuff" to help with kernel
rummaging was posted to alt.sources in May 1991 and is also
available via anonymous ftp as
usenet/alt.sources/articles/{329{6,7,8,9},330{0,1}}.Z from
wuarchive.wustl.edu.)
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