Static Link or Dynamic linked?

how can you tell whether a program is statically linked? And if it is dynamically linked, how do you know what libraries it needs?
The ldd command can answer both questions

shiv@ubuntu:~$ ldd /sbin/ldconfig
        not a dynamic executable (ldconfig is not dynmic loadable)

shiv@ubuntu:~$ ldd /bin/ln (ln is dynamic loadable but it needs below listed things to run)
        linux-gate.so.1 => (0x00918000)
        libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0x00110000)
        /lib/ld-linux.so.2 (0x0033f000)

ldconfig
------------
you use the ldconfig command without parameters to rebuild ld.so.cache

ldconfig -p | less to display ld.so.cache
how does the dynamic loader know where to look for executables?
>>As with many things on Linux, there is a configuration file in /etc.

shiv@ubuntu:~$ cat /etc/ld.so.conf
include /etc/ld.so.conf.d/*.conf

shiv@ubuntu:~$ ls /etc/ld.so.conf.d/*.conf | more
/etc/ld.so.conf.d/GL.conf
/etc/ld.so.conf.d/i486-linux-gnu.conf
/etc/ld.so.conf.d/libasound2.conf
/etc/ld.so.conf.d/libc.conf
/etc/ld.so.conf.d/vmware-tools-libraries.conf
shiv@ubuntu:~$

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C Program to Simulate Linux Cat command

/* * C program to Simulate Implementation of Linux *cat* command * This program will not handle redirection * you can try to improve this program to handle redirection of file contents */ #include<stdio.h> #include<string.h> #define MAX_FILE_NAME_CHARS 255 int main(int argc, char *argv[]) { FILE *fp; char file_name[MAX_FILE_NAME_CHARS], ch; int i; /* * after creating a.out, rename it as mycat for our own cat command * and it usage is same as standard cat command */ if(argc<1){ printf("Usage mycat <filename> \n"); return 0; } /* * cat handles more than one file * so we need this loop to handle all the files provided * on command line */ for(i=1; i<=argc;i++){ /* no need of copy but for understanding purpose, i have created * string for each file name */ strncpy(file_name, argv[i], MAX_FILE_NAME_CHARS); fp=fopen(file_name, "r"); if(fp == NULL) {

simple program to create Orphan process

shiv@ubuntu:~/ds/unix$ cat orp.c /* * Program to create orphan process @ Linux * getpid() gives process PID and * getppid() gives process's parent ID * here main() process ID is parent id is current shells PID * once process becomes orphan it is adopted by init process(it's PID is 1) */ #include<stdio.h> #include<unistd.h> int main() { pid_t p; /* create child process */ p=fork(); if(p==0) { /* fork() returns Zero to child */ sleep(10); } printf("The child process pid is %d parent pid %d\n", getpid(), getppid()); /*parent/child waits for 20 secs and exits*/ sleep(20); printf("\nProcess %d is done its Parent pid %d...\n", getpid(), getppid()); return 0; } O/p shiv@ubuntu:~/ds/unix$ ./a.out The child process pid is 2575 parent pid 1922 The child process pid is 2576 parent pid 2575 Process 2575 is done its Parent pid 1922... shiv@ubuntu:~/ds/unix$ Process 2576 is done its Parent pid 1...

Interactive C program to implement stack using doubly linked list

shiv@ubuntu:~/ds/stack$ cat stack.c /* * Copy right by Shiv Yaragatti * you are free to use, modify and redistribute code on own risk * Interactive C Program to implement STACK using Doubly linked list */ #include "header.h" struct stack { int data; struct stack *next; struct stack *prev; }; typedef struct stack *S; /*Push elements in to stack */ void push(S *stack) { int e; S temp; temp=malloc(sizeof(struct stack)); if(!temp){ printf("Can't allocate memory\n"); return; } printf("Enter element to push\n"); scanf("%d", &e); temp->data=e; if(*stack == NULL){ temp->next = temp->prev = NULL; *stack=temp; } else { temp->next = *stack; (*stack)->prev = temp; temp->prev = NULL; *stack=temp; } } /* Display elements in the stack */ void display(S s){ S temp; temp=s; printf("Elements are ...\n"); while(temp) { printf("%d\n", temp->data

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