Copy standard input to each FILE, and also to standard output.
A special variant of the tee for the shell is called script and permits
duplicating all input commands submitted to a shell into a file.
stat – display file or file system status
A UNIX Command stat -f /
$stat -f /
File: "/"
ID: bc427fdafb7b0541 Namelen: 255 Type: ext2/ext3
Block size: 4096 Fundamental block size: 4096
Blocks: Total: 18864769 Free: 16209639 Available: 15251363
Inodes: Total: 4792320 Free: 4684854
$
UNIX Explanation
Display file or file system status.
Related Source Code Exposition
static bool
do_statfs (char const *filename, bool terse, char const *format)
{
STRUCT_STATVFS statfsbuf;
if (STATFS (filename, &statfsbuf) != 0)
{
error (0, errno, _("cannot read file system information for %s"),
quote (filename));
return false;
}
if (format == NULL)
{
format = (terse
? "%n %i %l %t %s %S %b %f %a %c %d\n"
: " File: \"%n\"\n"
" ID: %-8i Namelen: %-7l Type: %T\n"
"Block size: %-10s Fundamental block size: %S\n"
"Blocks: Total: %-10b Free: %-10f Available: %a\n"
"Inodes: Total: %-10c Free: %d\n");
}
print_it (format, filename, print_statfs, &statfsbuf);
return true;
}
Source Code Highlight
Stat the file system and print what we find.
Featured Image
Related Knowledge
Due to shell aliases and built-in `stat' command, using an unadorned `stat' interactively or in a script may get you different functionality than that described here. Invoke it via `env' (i.e., `env stat ...') to avoid interference from the shell.
stat
Display file or file system status.
vmstat – Report virtual memory statistics
A UNIX Command . vmstat -m
Cache Num Total Size Pages fat_inode_cache 23 23 688 23 fat_cache 102 102 40 102 isofs_inode_cache 0 0 656 12 udf_inode_cache 23 23 712 23 fuse_request 0 0 632 25 fuse_inode 0 0 768 21 dm_crypt_io 0 0 152 26 kcopyd_job 0 0 368 22 dm_uevent 0 0 2608 12 dm_rq_target_io 0 0 400 20 ext3_inode_cache 11017 12882 824 19 ext3_xattr 0 0 88 46 journal_handle 170 170 24 170 journal_head 36 36 112 36 revoke_table 256 256 16 256 revoke_record 128 128 32 128 UDPLITEv6 0 0 1024 16 UDPv6 16 16 1024 16 tw_sock_TCPv6 0 0 320 12 TCPv6 17 17 1856 17 cfq_queue 110 119 240 17 Cache Num Total Size Pages bsg_cmd 0 0 312 13 mqueue_inode_cache 18 18 896 18 hugetlbfs_inode_cache 13 13 624 13 dquot 0 0 256 16 dnotify_mark 237 240 136 30 pid_namespace 15 15 2112 15 user_namespace 0 0 1072 15 posix_timers_cache 23 23 176 23 UDP-Lite 0 0 832 19 ip_fib_hash 46 46 88 46 arp_cache 36 72 320 12 RAW 450 475 832 19 UDP 19 19 832 19 tw_sock_TCP 16 16 256 16 TCP 24 38 1664 19 blkdev_queue 18 18 1736 18 blkdev_requests 34 44 360 22 bip-256 7 7 4224 7 bip-128 0 0 2176 15 bip-64 0 0 1152 14 bip-16 21 21 384 21 Cache Num Total Size Pages sock_inode_cache 531 575 704 23 file_lock_cache 22 22 184 22 net_namespace 12 12 2560 12 shmem_inode_cache 708 740 816 20 Acpi-ParseExt 1385 1400 72 56 Acpi-Namespace 816 816 40 102 task_delay_info 263 324 112 36 taskstats 23 24 328 12 proc_inode_cache 1240 1656 656 12 sigqueue 25 25 160 25 bdev_cache 19 19 832 19 sysfs_dir_cache 16424 16524 80 51 inode_cache 1175 1573 608 13 dentry 8128 9744 192 21 buffer_head 149614 206505 104 39 vm_area_struct 13975 14520 184 22 mm_struct 101 119 960 17 files_cache 105 115 704 23 signal_cache 143 165 1088 15 sighand_cache 140 165 2112 15 task_struct 252 288 1728 18 Cache Num Total Size Pages anon_vma 6242 6834 40 102 shared_policy_node 9171 10115 48 85 numa_policy 170 170 24 170 radix_tree_node 19547 19558 568 14 idr_layer_cache 453 465 544 15 dma-kmalloc-8192 0 0 8192 4 dma-kmalloc-4096 0 0 4096 8 dma-kmalloc-2048 0 0 2048 16 dma-kmalloc-1024 0 0 1024 16 dma-kmalloc-512 16 16 512 16 dma-kmalloc-256 0 0 256 16 dma-kmalloc-128 0 0 128 32 dma-kmalloc-64 0 0 64 64 dma-kmalloc-32 0 0 32 128 dma-kmalloc-16 0 0 16 256 dma-kmalloc-8 0 0 8 512 dma-kmalloc-192 0 0 192 21 dma-kmalloc-96 0 0 96 42 kmalloc-8192 11 12 8192 4 kmalloc-4096 582 616 4096 8 kmalloc-2048 233 272 2048 16 Cache Num Total Size Pages kmalloc-1024 596 656 1024 16 kmalloc-512 493 544 512 16 kmalloc-256 696 816 256 16 kmalloc-128 790 864 128 32 kmalloc-64 3047 3840 64 64 kmalloc-32 777 1024 32 128 kmalloc-16 2778 2816 16 256 kmalloc-8 4094 4096 8 512 kmalloc-192 5795 6489 192 21 kmalloc-96 649 798 96 42 kmem_cache 42 42 192 21 kmem_cache_node 128 128 64 64
UNIX Explanation
vmstat reports information about processes, memory, paging, block IO, traps, disks and cpu activity.
Related Source Code Exposition
int main(int argc, char *argv[]) {
char *partition = NULL;
int c;
while((c = getopt(argc, argv, "VdafmDnp:S:s")) != EOF) switch(c) {
case 'V':
display_version();
exit(0);
case 'd':
statMode |= DISKSTAT;
break;
case 'a':
/* active/inactive mode */
a_option=1;
break;
case 'f':
// FIXME: check for conflicting args
fork_format();
exit(0);
case 'm':
statMode |= SLABSTAT;
break;
case 'D':
statMode |= DISKSUMSTAT;
break;
case 'n':
/* print only one header */
moreheaders=FALSE;
break;
case 'p':
statMode |= PARTITIONSTAT;
partition = optarg;
if (memcmp(partition, "/dev/", 5) == 0) partition += 5;
break;
case 'S':
switch(optarg[0]) {
case 'b': case 'B': dataUnit = UNIT_B; break;
case 'k': dataUnit = UNIT_k; break;
case 'K': dataUnit = UNIT_K; break;
case 'm': dataUnit = UNIT_m; break;
case 'M': dataUnit = UNIT_M; break;
default:
fprintf(stderr, "-S requires k, K, m or M (default is kb)\n");
exit(EXIT_FAILURE);
}
szDataUnit[0] = optarg[0];
break;
case 's':
statMode |= VMSUMSTAT;
break;
default:
/* no other aguments defined yet. */
usage();
}
Source Code Highlight
Using getopt to select -m option for slabinfo.
Featured Image
Related Knowledge
Physical memory the actual RAM installe is a finite resource on any system. The Linux memory handler manages the allocation of that limited resource by freeing portions of physical memory when possible. All processes use memory, of course, but each process doesn't need all its allocated memory all the time. Taking advantage of this fact, the kernel frees up physical memory by writing some or all of a process' memory to disk until it's needed again. The kernel uses paging and swapping to perform this memory management. Paging refers to writing portions, termed pages, of a process' memory to disk. Swapping, strictly speaking, refers to writing the entire process, not just part, to disk. In Linux, true swapping is exceedingly rare, but the terms paging and swapping often are used interchangeably. When pages are written to disk, the event is called a page-out, and when pages are returned to physical memory, the event is called a page-in.A page fault occurs when the kernel needs a page, finds it doesn't exist in physical memory because it has been paged-out, and re-reads it in from disk. Page-ins are common, normal and are not a cause for concern. For example, when an application first starts up, its executable image and data are paged-in. This is normal behavior. Page-outs, however, can be a sign of trouble. When the kernel detects that memory is running low, it attempts to free up memory by paging out.Though this may happen briefly from time to time, if page-outs are plentiful and constant, the kernel can reach a point where it's actually spending more time managing paging activity than running the applications, and system performance suffers. This woeful state is referred to as thrashing. Using swap space is not inherently bad. Rather, it's intense paging activity that's problematic. For instance, if your most-memory-intensive application is idle, it's fine for portions of it to be set aside when another large job is active. Memory pages belonging to an idle application are better set aside so the kernel can use physical memory for disk buffering. source : http://www.linuxjournal.com/article/8178
<!– Slab Allocation
Linux Slab Allocator. –!>
vmstat -m
vmstat reports information about processes, memory, paging, block IO, traps, disks and cpu activity.
Slab Allocation
Linux Slab Allocator.
ypdomainname – show or set the system’s NIS/YP domain name
ABOUT NIS
The Network Information Service, or NIS (originally called Yellow Pages or YP), is a client–server directory service protocol for distributing system configuration data such as user and host names between computers on a computer network. Sun Microsystems developed the NIS; the technology is licensed to virtually all other Unix vendors. Because British Telecom PLC owned the name "Yellow Pages" as a registered trademark in the United Kingdom for its paper-based, commercial telephone directory, Sun changed the name of its system to NIS, though all the commands and functions still start with "yp". A NIS/YP system maintains and distributes a central directory of user and group information, hostnames, e-mail aliases and other text-based tables of information in a computer network. For example, in a common UNIX environment, the list of users for identification is placed in /etc/passwd, and secret authentication hashes in /etc/shadow. NIS adds another "global" user list which is used for identifying users on any client of the NIS domain. Administrators have the ability to configure NIS to serve password data to outside processes to authenticate users using various versions of the Unix crypt(3) hash algorithms. However, in such cases, any NIS(0307) client can retrieve the entire password database for offline inspection. Kerberos was designed to handle authentication in a more secure manner.
TYPICAL COMMAND LINE SESSION RELATED
[bash]
$ypdomainname
ypdomainname: Local domain name not set
$ypdomainname beautifulwork.edu
ypdomainname: you must be root to change the domain name
$dnsdomainname
Jeff
$ypdomainname
ypdomainname: Local domain name not set
$sudo ypdomainname beautifulwork.edu
$ypdomainname
beautifulwork.edu
$
[/bash]
LINK
https://linux.die.net/man/1/ypdomainname
https://en.wikipedia.org/wiki/Network_Information_Service
ypdomainname
commands used to display or set domain name , hostname and YP domain name.
backtrace for iceweasel related hangup
(gdb) bt #0 0x00007fc68928b99d in pthread_join (threadid=1404900385100136, thread_return=0x0) at pthread_join.c:89 #16 0x00007fc68773d8e8 in XRE_main (argc=, argv=, aAppData=) at nsAppRunner.cpp:3331 #17 0x00000000004024df in main (argc=1, argv=0x7fffaa9352c8) at nsXULStub.cpp:493
iceweasel related hangup
(gdb) bt
#0 0x00007fc68928b99d in pthread_join (threadid=140490038565136, thread_return=0x0) at pthread_join.c:89
#16 0x00007fc68773d8e8 in XRE_main (argc=, argv=, aAppData=) at nsAppRunner.cpp:3331
#17 0x00000000004024df in main (argc=1, argv=0x7fffaa9352c8) at nsXULStub.cpp:493
getopt – parse command options
commandline session $getopt hello -- $getopt hello how are you ? -- how are you 1 c h $getopt hello hello are you ? -- hello are you 1 c h $getopt hello hello are yours ? -- hello are yours 1 c h $getopt hello hello are yours what ? -- hello are yours what 1 c h $getopt hello hello are yours what -- hello are yours what $getopt hello hello are yours what ! -- hello are yours what ! $getopt hello hello are yours what $ -- hello are yours what $ THEORY DROP getopt is used to break up (parse) options in command lines for easy parsing by shell procedures, and to check for legal options.