thomas@sky.COM (Jim Thomas) (11/03/88)
I want to append data to an a.out file. Then I want the executing program to read the data (which, of course, would have been ignored by the exec itself). From an executing program how do I open the a.out file that was exec'd? That's easy -- get its pathname. One way to get that pathname (i.e., the first argument to execxx, not argv[0]) is to search process, text, and in-core inode tables to get the inode number plus major and minor device numbers and then to search the directories in the corresponding file system. Too time-consuming. Is there a better way? Is the FIRST argument to execxx squirreled away somewhere? If someone would suggest how to write a program that would QUICKLY find the FULL pathname of its exec'd a.out file, regardless which directory the a.out file happened to be installed in, I'd be grateful. I'm currently using SunOS 3.5. Jim Thomas uunet!swan.ulowell.edu!sky!thomas SKY Computers Inc., Foot of John Street, Lowell, MA 01852 (508)454-6200
guy@auspex.UUCP (Guy Harris) (11/04/88)
>Is the FIRST argument to execxx squirreled away somewhere?
No.dlm@cuuxb.ATT.COM (Dennis L. Mumaugh) (11/05/88)
In article <395@auspex.UUCP> guy@auspex.UUCP (Guy Harris) writes: >>Is the FIRST argument to execxx squirreled away somewhere? > >No. Actually, Guy isn't exactly correct. The kernel does remember part of the name of the a.out used in the exec for accounting purposes. The last part of the path (i.e. the file name but not path and directory) is saved in the ublock. The kernel accounting writes this and other information into a file on the process's exit. This information is also in a program's core dump. [Useful if you find random cores in / ]. But if you mean "Can my process find out the name of the file that was used for execution?" Guy is right. Only if one has a /proc file system ala System V Release 3.1.1 for the 3B15 or Version 8/9 can one get this information and then it isn't easy and one must be root. [ Of course if you are root, then you can read /dev/kmem and reverse engineer the exec and find out. A 45 on the Knuth Scale of difficulty. ] -- =Dennis L. Mumaugh Lisle, IL ...!{att,lll-crg}!cuuxb!dlm OR cuuxb!dlm@arpa.att.com