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Other File Flags in Software Integration barcode pdf417 in Software Other File Flags

11.3.2.5 Other File Flags using barcode generation for software control to generate, create pdf 417 image in software applications. interleaved 25 Other ags are maintain Software pdf417 ed in the per-process le descriptor and are not pushed down to the le structure. The ags that are used at the le descriptor level are mostly for the operating system to use they are not user settable. One such ag is FCLOEXEC: the close-on-exec ag.

This ag noti es the operating system to close the le descriptor in the new process if a process executes an exec(2) call. Normally, all open les are inherited by child processes, which is not always the desired behavior. The kernel implements FCLOEXEC with a simple close_exec() kernel routine called from exec(2).

close_exec() walks through the le descriptor array and closes any le with the FCLOEXEC ag set. The fcntl(2) call sets, clears, and examines the le descriptor s ag eld. Currently, FCLOEXEC is the only ag that can be set, cleared, or examined.

. 11.3.2.6 The dup System Call The dup(2) system call PDF-417 2d barcode for None allows us to duplicate a le descriptor, such that two le descriptors point to the same le structure entry. We indicated earlier that an open(2) call will fetch a new le descriptor and result in a new le structure getting allocated, even if the process already has the same le opened. dup(2) duplicates a le descriptor and will result in a new uf_entry structure for the le descriptor.

The difference is that the uf_ofile pointer, which points to le struc-. Solaris Files and File I/O ture, will point to the Software barcode pdf417 same le structure as the dup ed le descriptor. A new le structure is not created, as would be the case with a second open(2) of the same le. dup(2) is useful for situations where the programmer wants multiple references to the same le to share the same view of the current le offset.

Since the current le pointer (byte offset) is maintained in the le structure, dup d le descriptors share a common view of the le s offset. Consider a test program, ofd (code not shown), that does two opens of the same le. The second open sets the O_SYNC ag (which we added only to demonstrate how these le structure ags can be examined).

After the two opens, a dup(2) is executed to duplicate the second le descriptor. Below is some output and an example of using /usr/proc/bin/pfiles to look at a process s open les..

$ ofd & [1] 24788 fawlt y> fd1: 3, fd2: 4,dfd: 5 $ /usr/proc/bin/pfiles 24788 24788: ofd Current rlimit: 64 file descriptors 0: S_IFCHR mode:0620 dev:32,0 ino:324208 uid:20821 gid:7 rdev:24,1 O_RDWR 1: S_IFCHR mode:0620 dev:32,0 ino:324208 uid:20821 gid:7 rdev:24,1 O_RDWR 2: S_IFCHR mode:0620 dev:32,0 ino:324208 uid:20821 gid:7 rdev:24,1 O_RDWR 3: S_IFREG mode:0755 dev:32,8 ino:18 uid:20821 gid:30 size:0 O_RDWR 4: S_IFREG mode:0755 dev:32,8 ino:18 uid:20821 gid:30 size:0 O_RDWR. O_SYNC 5: S_IFREG mode:0755 dev:32,8 ino:18 uid:20821 gid:30 size:0 O_RDWR O_SYNC On the rst line, we ca pdf417 2d barcode for None n see that the test program prints the three open le descriptor values after the open(2) and dup(2) calls have executed. Every process already has le descriptors 0, 1, and 2 allocated, and as a result, the two open les and dup ed le are le descriptors 3, 4, and 5. The pfiles command dumps some information on process open les, and we see that fd 4 and fd 5 have the O_SYNC ag set, which is logical because they re both referencing the same le structure.

. System File I/O Now, we use crash(1M) to illustrate the le structure sharing in our test program. # /etc/crash dumpfile = /dev/mem, namelist = /dev/ksyms, outfile = > p 59 PROC TABLE SIZE = 1962 SLOT ST PID PPID PGID SID UID PRI NAME 59 r 24774 24716 24774 24716 20821 0 ofd > u 59 PER PROCESS USER AREA FOR PROCESS 59 PROCESS MISC: command: ofd, psargs: ofd start: Tue Apr 21 21:55:51 1998 mem: 43449, type: exec vnode of current directory: 60025394 OPEN FILES, POFILE FLAGS, AND THREAD REFCNT: [0]: F 0x60b6eca8, 0, 0 [1]: F 0x60b6eca8, 0, [2]: F 0x60b6eca8, 0, 0 [3]: F 0x60824c58, 0, [4]: F 0x60824870, 0, 0 [5]: F 0x60824870, 0, > f 60824c58 ADDRESS RCNT TYPE/ADDR OFFSET FLAGS 60824c58 1 UFS /608ba0e8 0 read write > f 60824870 ADDRESS RCNT TYPE/ADDR OFFSET FLAGS 60824870 2 UFS /608ba0e8 0 read write.
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