The lshw command

The lshw command lists the hardware information in your system. I came across this because I was having issues with wifi connectivity in Ubuntu 12.04. It just keeps disconnecting after a while and connects back. So, wanted to check the wifi card on and look for possible solutions.

root@Imperfecto_:~# lshw
imperfecto_               
    description: Desktop Computer
    product: Parrot ()
    vendor: GOOGLE
    version: 1.0
    serial: 123456789
    width: 64 bits
    capabilities: smbios-2.7 dmi-2.7 vsyscall32
    configuration: boot=normal chassis=desktop
  *-core
       description: Motherboard
       physical id: 0

and so on...

And I was interested in my wifi card, so I gave it some filters

root@Imperfecto_:~# lshw -C network
  *-network               
       description: Wireless interface
       product: AR9462 Wireless Network Adapter
       vendor: Atheros Communications Inc.
       physical id: 0
       bus info: pci@0000:01:00.0
       logical name: wlan0
       version: 01

and so on...

Installing the gnome desktop in Ubuntu 12.04

Yeah, I also didn't like the Unity which comes by default in Ubuntu 12.04. Just install the gnome-session-fallback and you are good to go

sudo apt-get install gnome-session-fallback

#In the newer version you may want to try

sudo apt-get install gnome-session-flashback

agentBUSH@ChrUbuntu:~# sudo apt-get install gnome-session-fallback
Reading package lists... Done
... bla bla bla ...
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place
agentBUSH@ChrUbuntu:~# 

After installation, log out and at the log-in screen you will have the gnome-classic.

How does httpd serves multiple client listening on a single port 80?

Take a look at this post

Program to print pattern

Program to print the following pattern (see below for the pattern). More patterns will be posted later.

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#include "stdio.h" #include "stdlib.h" #include "string.h" static void print_it(unsigned len) { if(!len) return; unsigned i; char *star, *buf, fmt[16]=""; star = malloc(sizeof(char) * len+1); if(!star) return; buf = malloc(sizeof(char) * len+1); if(!buf) return; for(i=0; i<len; i++) strcat(star, "*"); snprintf(fmt, 16, "%%%ds\n", len); for(i=len; i>0; i--){ strcpy(buf, star+i-1); printf(fmt, buf); } free(star); free(buf); return; } int main(int argc, char **argv) { print_it(12); return 0; }

[root@Imperfecto_1 ~]gcc run.c && ./a.out
           *
          **
         ***
        ****
       *****
      ******
     *******
    ********
   *********
  **********
 ***********
************

Valgrind Output

[root@Imperfecto_1 ~]valgrind ./a.out

==5472== HEAP SUMMARY:
==5472==     in use at exit: 0 bytes in 0 blocks
==5472==   total heap usage: 2 allocs, 2 frees, 26 bytes allocated
==5472== 
==5472== All heap blocks were freed -- no leaks are possible

Split functionality of awk implementation in C

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#include "stdio.h" #include "stdlib.h" #include "string.h" static unsigned split(const char *in, char ***t_out, const char *delim) { if( !*in || !*delim ){ return 0; } unsigned i_len = strlen(in); char *buf = NULL; char *ptr = NULL; unsigned t_len, i=0; buf = malloc(sizeof(char) * i_len); if(!buf) return 0; if(!memcpy(buf, in, i_len)) return 0; ptr = strtok(buf, delim); if(ptr) { t_len = strlen(ptr); *t_out = (char **)malloc(sizeof(char*)); (*t_out)[0] = (char *)malloc(sizeof(char) * t_len); memcpy((*t_out)[0], ptr, t_len); } while(ptr){ ptr = strtok(NULL, delim); if(ptr) { i++; t_len = strlen(ptr); *t_out = (char **)realloc(*t_out, sizeof(char *) * (i+1)); (*t_out)[i] = (char *)malloc(sizeof(char) * t_len); memcpy((*t_out)[i], ptr, t_len); } } free(buf); return i; } int main(int argc, char **argv) { char *in = "split.implementation.of.awk"; char **out = NULL; int i, len = split(in, &out, "."); if(out) { for(i=0; i<=len; i++){ printf("%s\n", out[i]); free(out[i]); } free(out); } return 0; }

[root@Imperfecto_1 ~] gcc -g run.c && ./a.out
split
implementation
of
awk

Valgrind output

[root@Imperfecto_1 ~]# valgrind ./a.out
==2320== malloc/free: in use at exit: 0 bytes in 0 blocks.
==2320== malloc/free: 9 allocs, 9 frees, 91 bytes allocated.
==2320== For counts of detected errors, rerun with: -v
==2320== All heap blocks were freed -- no leaks are possible.

Reverse bits in an Integer

A simple function to reverse the bits in an integer

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#include "stdio.h" #include "stdlib.h" /* Function to reverse the bits * Assuming 32 bits. * Simple functionality, get the last bit by right shift * and insert into the output by ORing and then left shifting. * There are better ways to do this. */ void reverse(unsigned *input) { unsigned i=0, mask=0x1, res=0x0, tmp = 0x0; unsigned in = *input; for(i=0; i<32; i++){ tmp = in & mask; in = in >> 1; res = res << 1; res |= tmp; } *input = res; return; } int main(int argc, char **argv) { unsigned input = 0xffffbbbb; printf("%x\n", input); reverse(&input); printf("%x\n", input); return 0; }

[root@Imperfecto_1 ~] gcc run.c && ./a.out
ffffbbbb
ddddffff

[root@Imperfecto_1 ~] echo "ibase=16;obase=2; FFFFBBBB" | bc
11111111111111111011101110111011

[root@Imperfecto_1 ~] echo "ibase=16;obase=2; DDDDFFFF" | bc
11011101110111011111111111111111

Convert IP to Integer

Formula would be :-

First Octet * (256 ^ 3) + Second Octet * (256 ^ 2) 
+ Third Octet * (256 ^ 1) + Fourth Octet

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#include "stdio.h" #include "math.h" /* Function to convert IP address into Integer * Input : IP address array * Output : Converted IP */ unsigned int ip_to_int(unsigned in[]) { return ((in[0]*(pow(256,3))) + (in[1]*(pow(256,2))) + (in[2]*(pow(256,1))) + (in[3])); } int main(int argc, char **argv) { unsigned ip_addr[] = { 192, 168, 1, 124 }; printf("Input : %d.%d.%d.%d\n", ip_addr[0], ip_addr[1], ip_addr[2], ip_addr[3]); printf("Output : %u\n", ip_to_int(ip_addr)); return 0; }

[root@Imperfecto_1 ~] gcc run.c && ./a.out
Input  : 192.168.1.124
Output : 3232235900

sshd in chrubuntu

Looks like ChrUbuntu (Chrome + Ubuntu) also doesn't come with sshd installed. Let us install it.

apt-get install openssh-server

If your are not the root, use sudo

sudo apt-get install openssh-server

Post installation it runs the sshd service by default.
Verify it

root@ChrUbuntu:~# ps -eaf | grep sshd
root     14580     1  0 21:58 ?        00:00:00 /usr/sbin/sshd -D

Or start the service, either by

root@ChrUbuntu:~# /etc/init.d/ssh start

or by

root@ChrUbuntu:~# service ssh start

That is all it takes ;)

To print the buffer in HEX

Nothing big, thought I will add this for my own reference. This will print the buffer in hex.

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static void print_buffer(unsigned *buffer, int len) { unsigned i = 0; for(i=0;i<len;i++){ if(!(i%8)) printf("\n "); printf(" 0x%02x",buffer[i]); } return; }

You should get an output something like this based on your input

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0x74 0x65 0x73 0x74 0x20 0x6c 0x61 0x62 0x65 0x6c 0xa0 0xba 0x9f 0x93 0x6c 0xda 0x31 0x18 0x27 0xa6 0xf7 0x96 0xff 0xd5

Hope this helps someone.