Commands & tool for working in C environment

Cscope

·         find . -name "*.c" -o -name "*.cpp" -o -name "*.h" -o -name "*.xml" -o -name "Makefile" -name "makefile" > cscope.files

·         cscope -q -R -b -i cscope.files

·         ctags -L cscope.files   -> this is working.

Vim:

·         To move next line based on previous line

o    Set cintend

·         To highlight the white space

/\s\+$

:set hlsearch

Or  

:match Error /\s\+$/

·         To count the selected word

o    :%s/pattern//gn

·         Replance from current cursor position:

o    .,$s/conn/connLow/gc     => "."  is considered as the current position.

·         Diff in the console with | symbol to notify diff, not vimdiff, tool is diff

o    diff -y summary.txt -y output/summary.txt

·         Control+W followed by W to toggle between open windows and,

Notepad ++:

·         Short cut for go to specific line

o    Ctrl + g

o    To block select like VIM, similar to ctrl + v in VIM

o    ctrl + alt + shift and then left click mouse

Coverity:

1.       Coverity line between 2 diff with duplicate lines

Replace branch name in another file

sort tmp_857 | uniq -c > sort_tmp_857

sort tmp_fresh | uniq -c > sort_temp_fresh

vimdiff sort_tmp_fresh  sort_tmp_857

Find:

·         To list the extention of file from this path

o    find . -type f -name "*.*" | awk -F. '{print $NF}' | sort -u

·         To list specific file

o    find -regex ".*\.\(jpg\|gif\|png\|jpeg\)"

Grep:

·         To display a multiple pattern

grep -E 'foo|bar' *.txt

EG: Top command to display 2 var=> top | grep -E 'Mem|CPU|tcpdump|Load'

·         To search backslash

grep -r \\\\ *

·         To list only the file name

grep -l

·         To display the next 3 line from the founded word

grep -A 3 FORWARD_NULL folder_name_857.txt

·         To display line before & After

o    grep's -A 1 option will give you one line after;

o    -B 1 will give you one line before;

o     -C 1combines both to give you one line both before and after.

·         To search only header files:

o    grep -ri --include \*.h *

X11 -> display

Xauth list -> to list the authenticate cookies

Below command to remove all entries in xauth to resolve "X11 proxy: MIT-MAGIC-COOKIE-1 data did not matchError" Error

 xauth list | cut -f1 -d\  | xargs -i xauth remove {}

LS:

To list the KB or MB

Ls --block-size=k for KB,

Ls --block-size=m for MB.

Other Unix command:

·         To list the file details

file -L /usr/lib/libpcap.so.1

·         du -sh * => will display the all folder with used size

·         du -sh * | sort -h   ==> to sort in order.

·         lsb_release -a => to know the Ubuntu version(Eg: 14.0)

·         Convert Linux txt file into windows format:

o     perl -p -e 's/\n/\r\n/' < test > dosfile3.txt

·         Empty the contents of a file:

o    cp /dev/null <file Name to empty>

·         Remove the stray value " error: stray ‘\302’ in program" or error: stray ‘\240’ in program from .c file.

o    tr -cd '\11\12\15\40-\176' < old.c > new.c

·         Unzip the file:

o    Run file access-2.log.gz, it will tell you the compression type.

·         EG: $file tmp.gz

         tmp.gz: 8086 relocatable (Microsoft)

·         To know the default gateway

ip route | grep default

·         To know the DNS is resolving or not

o    nslookup google.com   => It should return the google.com ip

·         Iptables & conntrack

o    To list the conntrack entries

·         conntrack –L

·         conntrack -L -p tcp --dport 80

o    To delete the entries in conntrack

·         conntrack -D

o    To delete Input rule

·         iptables -L -n -v --line-number

·         iptables -D INPUT 3

o    To delete POSTROUTING:

·         iptables -t nat -L -n -v --line-number

·         iptables -t nat -D POSTROUTING 2

o    Command to list:

·         iptables -L

·         iptables -L -n  => For INPUT, FORWARD and OUTPUT-chains

·         iptables -L -t nat

·         iptables -t nat -L -n -v  -> to View nat rules

Screen:

          screen -S <user name> => To create a new screen.

screen -x <name>   => To open an existing screen.

screen -ls    => To list the available screen

ctrl + a+c   => to create a new window inside the screen.

ctrl +a + d  => To come out from the screen.

Ctrl + a + A  => To rename the current window.

F1      => move backside window inside the screen

F2      => Move forward window inside the screen.

Screen -L -x <name >   => Open the session with saving the logs in home dir.

Tools:

Ss->  socket statistics.

netstat command reads various /proc files but ss gets its information directly from kernel space, so good.

ss -ap | grep high => give the ipc socket details with process id.

-u => udp   (IPC socket is not udp because it don’t have any layer 3 IP)

-t => tcp

-a => all

Visio -> is a tool for msoffice to use UML diagram.

nm -> to find the function name in binary =>  nm -A nsh  | grep nsh_sdb_connect

Objdump -> used to find function name but our ARM architecture not supporting.

arm-elf-objdump -> not installed

arm-elf-objdump -D -b binary -marm binaryfile.dat

Ldd:

You can list the shared library dependencies which your executable is dependent

abuser@labuser-virtual-machine:~/velrajk/sample/ipc_soc/API$ ldd cli

        linux-vdso.so.1 =>  (0x00007ffd4d38e000)

        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f6c03f7b000)

        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f6c03bb3000)

        /lib64/ld-linux-x86-64.so.2 (0x00007f6c04199000)

labuser@labuser-virtual-machine:~/velrajk/sample/ipc_soc/API$

·         Wing ftp:

o    It’s a trial software supports ftps server.

o    Create new domin &  new user, give the ftp directory path while creating user.

o    Domain is the FTP server or HTTP server running port

o    User is the ftp login username, while connecting to this ftp need to give this user details for login.

o    Windows defender firewall or any firewall on windows PC should be disabled.

Linux troubleshoot:

Firefox not opening:

sudo chown labuser:labuser .Xau*

rm .Xauthority-c

rm .Xauthority-1

count character, line & word in the file using c program

Note:

•  For getchar should not use char datatype, because it may return EOF.
• The value for EOF is -1

Program:

#include <stdio.h>
#include <errno.h>

#define WORD_OUTSIDE 1   /* Word outside */
#define WORD_INSIDE  0   /* Word inside  */

int main(int argc, char *argv[])
{
        /* For getchar should not use char datatype, because it return EOF.
         * The value for EOF is . */
        int   ch = 0, nc = 0, nl = 0, nw = 0, word_in_out;
        FILE  *fp_input = NULL;

        if (argc <=1) {
                printf("Give file name in the command prompt while executing the commmand: \n\n");
                return 0;
        }

        fp_input = fopen(argv[1], "r");
        if (fp_input == NULL) {
                printf("Failed to open the file %d. \n\n", errno);

                perror("Error:");
                return 0;
        }

       word_in_out = WORD_OUTSIDE;
        while ((ch = fgetc(fp_input)) != EOF) {
                ++nc;
                if (ch == '\n') {
                        ++nl;
                }
                if ((ch == ' ') || (ch == '\n') || (ch == '\t')) {
                        word_in_out = WORD_OUTSIDE;
                } else if (word_in_out == WORD_OUTSIDE) {
                        ++nw;
                        word_in_out = WORD_INSIDE;
                }
        }

        printf("Total number of character = %d, Line = %d, word = %d \n",
                       nc, nl, nw);

        return 0;
}

Output:

velraj@velraj-HEC41:~/CProgram$ ./a.out new
Total number of character = 28, Line = 5, word = 7

Linked list add, delete & display

Program:

#include <stdio.h>
#include <stdlib.h> // for calloc

typedef struct node {
    struct node *next;
    int value;
}node_t;

node_t *root = NULL;

void line_80(char *str)
{
    int i;
    for (i = 0; i < 80; printf("%s", str), i++);
    printf("\n");
}

void display_list(void)
{
    node_t *temp = NULL;
    if (root == NULL) {
        printf("List is empty \n");
    }
    printf("\tThe available list value is: ");
    for (temp = root; temp ; temp = temp->next) {
        printf("%d ", temp->value);
        if (temp->next) {
            printf("-> ");
        }
    }
    printf("\n\n");
}

int insert_list(node_t  **root_node, int value)
{
    node_t  *temp = NULL;
    temp = (node_t *) calloc(1, sizeof(node_t));
    temp->value = value;
    if (*root_node == NULL) {
        *root_node = temp;
    } else {
        temp->next = *root_node;
        *root_node = temp;
    }
}
void delete_list(node_t **root_node, int value)
{
    node_t *temp = NULL, *prev = NULL;
    if (*root_node == NULL) {
        printf("List is empty, so could not delete any value \n");
        return;
    }
    for (temp = prev = *root_node; temp ; prev = temp, temp = temp->next) {
        if (temp->value == value) {
            if (temp == *root_node) {
                *root_node = temp->next;
            } else {
                prev->next = temp->next;
            }
            free(temp);
            temp = NULL;
            printf("Delete the node with value %d \n", value);
            return;
        }
    }
}

int main()
{
    int input, choice = 0, value = 0;

    while (1) {
        line_80("*");
        printf("\t 1. Display the list\n\t 2. Insert to list: \n\t 3.Delete from list\n");
        line_80("*");
        printf("\n\t Enter your choice: ");
        scanf("%d", &choice);
        if (choice <= 0 || choice >= 4) {
            printf("Please choose correct choice \n");
            continue;
        }
        switch(choice)
        {
            case 1:
                display_list();
            break;
            case 2:
                printf("Enter the value to insert:");
                scanf("%d", &value);
                insert_list(&root, value);
            break;
            case 3:
                printf("Enter the value to delete:");
                scanf("%d", &value);
                delete_list(&root, value);
            break;
            default:
                printf("Wrong choice, select correct choice \n");
        }
    }
}

Output:

learn$ ./a.out
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 1
List is empty
        The available list value is:
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 2
Enter the value to insert:1
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 2
Enter the value to insert:2
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 2
Enter the value to insert:3
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 1
        The available list value is: 3 -> 2 -> 1
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 3
Enter the value to delete:2
Delete the node with value 2
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 1
        The available list value is: 3 -> 1
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 3
Enter the value to delete:1
Delete the node with value 1
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 1
        The available list value is: 3
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 3
Enter the value to delete:3
Delete the node with value 3
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************
         Enter your choice: 1
List is empty
        The available list value is:
********************************************************************************
         1. Display the list
         2. Insert to list:
         3.Delete from list
********************************************************************************

Data type of pid_t is int

• /sys/types.h
• #ifndef __pid_t_defined
  typedef __pid_t pid_t;
  # define __pid_t_defined
  #endif
• bits/types.h
•  __STD_TYPE __PID_T_TYPE __pid_t;        /* Type of process identifications.  */# #define __STD_TYPE             typedef
• #define __PID_T_TYPE            __S32_TYPE
• #define __S32_TYPE              int
  

Strncmp usage from working

SYNOPSIS

#include <string.h>
 int strncmp(const char *s1, const char *s2, size_t n);

Description
The C library function int strncmp(const char *str1, const char *str2, size_t n) compares at most the first n bytes of str1 and str2.

RETURN VALUE
       The strcmp() and strncmp() functions return an integer less than, equal to, or greater than zero if s1 (or the first n bytes thereof) is found, respectively,  to  be  less  than,  to
       match, or be greater than s2.

• strncmp will be usefully only if the both strings are not null terminated, at that time only it will be useful to stop the comparison upto n.
• if we are using strlen to calculate lenght to give on  n, then strncmp is not useful.
• strncmp with strlen is as good as strcmp.
• Right way to use strncmp is to check for max allowed lenght.  we can use max size macro used to declare the string.

Convert Error no(errno) into a string value

NAME

       strerror, strerror_r - return string describing error number

SYNOPSIS

 #include <string.h>

       char *strerror(int errnum);

       int strerror_r(int errnum, char *buf, size_t buflen);

                   /* XSI-compliant */

       char *strerror_r(int errnum, char *buf, size_t buflen);

                   /* GNU-specific */

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       The XSI-compliant version of strerror_r() is provided if:

       (_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && ! _GNU_SOURCE

       Otherwise, the GNU-specific version is provided.

     

DESCRIPTION

• The strerror() function returns a pointer to a string that describes the error code passed in the argument errnum.
• For example, if errnum is EINVAL, the returned description will "Invalid argument".
• This string must not be modified by the application, but may be modified by a subsequent call to strerror()
• The  strerror_r()  function  is  similar to strerror(), but is thread safe. 

RETURN VALUE

    Return the appropriate error description string, or an "Unknown error nnn" message if the error number is unknown.

Program:

/* error number into an String value program by Velraj.K
   Check : http://velrajcoding.blogspot.in
  */


#include <stdio.h>
#include <errno.h>
#include <string.h>

int main()
{
    FILE *fp;

    /* first rename if there is any file */
    rename("file.txt", "newfile.txt");

    /* now let's try to open same file */
    fp = fopen("file.txt", "r");
    if( fp == NULL ) {
        perror("Error: ");
        printf("velraj errno = %d value (%s)\n", errno, strerror(errno));
        return(-1);
    }
    fclose(fp);

    return(0);

}

Output:

sample$ ./a.out
Error: : No such file or directory
velraj errno = 2 value (No such file or directory)

python - Split the file name from git diff

Program:

import sys   # For command line argument
import os.path # To check file existing

def generate_writefile(file_name):
    count = 1
    while True:                      # in True T must be capital
        file_name_new = file_name
        file_name_new += "_" + str(count)
        count += 1
        if not os.path.isfile(file_name_new):
            return file_name_new
        if count >=10 :
            print "Error while creating file"
            return None


def main():
    cmd_len = len(sys.argv)
    if(cmd_len <2):
        print "\t\tVel Error, provide the git file name\n\n"
        return

    name =  sys.argv[1]
    file_name = generate_writefile(sys.argv[1])
    if file_name == None:
        return
    file_write = open(file_name, 'w')
    if  not os.path.isfile(sys.argv[1]):
        print "Vel Error, provided file is not existing\n\n"
        return

    count_file = 0
    with open(sys.argv[1]) as openfileobject:
        for line in openfileobject:
            spl_for_com = line.split()      # convert the list of array into an separated string
            length = len(spl_for_com)
            if((length >=4) and (spl_for_com[0] == "diff") and (spl_for_com[1] == "--git")):
#        print "Got the match velraj ", spl_for_com[2][1:], spl_for_com[3]
                file_write.write(spl_for_com[2][1:])
                file_write.write("\n")
                count_file += 1
    print "Number of file = ", str(count_file), "Output file name is = ", file_name

    if count_file == 0:
        os.remove(file_name)

main()


# API to read from file.
    #    message = file_read.read()   # It read a whole file in  1 time
    #    message = file_read.readline()  # Its read only single line