Anatomy of Command Line Arguments in Linux

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Anatomy of command line arguments in Linux http://mylinuxbook.com/command-line-arguments-in-linux-part2/

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int main()

int main(int argc, char *argv[])

int execve(const char *filename, char *const argv[], char *const envp[]);


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#include < stdio.h >

int main(int arc, char* argv[])

{

int i = 0;

printf(Inside main\n); for (i = 0; i < argc; i++)

{

printf( %d-th argument received is %s\n, i, argv[i]);

}

return 0;

}

$gcc cmd.c -Wall -o cmd


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$./cmd --name Rupali --line 12

Inside main

0 argument received is ./cmd

1 argument received is --name

2 argument received is Rupali

3 argument received is --line

4 argument received is 12

th

th

th

th

th


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getopt_long()

unistd.h

getopt.h

int getopt(int argc, char * const argv[], const char *optstring);


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A f d li i Li h // li b k / d li i li 2/


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Command Option string used in getopt()

ls -lt lt

find -n flilename n:gcc -c -o output co:

mkdevice [options]

Options:

-c : Create a Device with name as provided

-k : The device node to be created with this device number


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A t f d li t i Li htt // li b k / d li t i li t2/


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$mkdevice -c mydevice

$mkdevice -k 3

$mkdevice -c mydevice -k 3

-co:

getopt(argc, argv,"-co:")

compiler main.c -c -o main


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A t f d li t i Li htt // li b k / d li t i li t2/


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#include

#include #include

#define MAXLEN 30

struct Device

{

char name[MAXLEN];

int number;

};

int main(int argc, char** argv)

{

char optc = 0;

struct Device dev = {"dev_0", 112};

int devNum = 0;

while ((optc = getopt(argc, argv,"c:k:")) != -1)

{

switch(optc)

{

case 'c': printf("Creating the device of name %s\n", optarg);

strncpy(dev.name, optarg, MAXLEN);

break;

case 'k':

devNum = atoi(optarg);

dev.number = devNum;

break;

default:


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Anatomy of command line arguments in Linux http://mylinuxbook com/command line arguments in linux part2/


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printf("Invalid Option!\n");

exit(0);

}

}

printf("Device %s created !\n", dev.name);

printf("Device : %s\n", dev.name);

printf("Number : %d\n", dev.number);

return 0;

$ gcc mkdevice.c -Wall -o mkdevice

$ ./mkdevice -c mlbdev -k 12

Creating the device of name mlbdev

Device mlbdev created !

Device : mlbdev

Number : 12



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#include

#include

#include

#define MAXLEN 30

struct Device

{

char name[MAXLEN];

int number;

};


{

char optc = 0;

struct Device dev = {"dev_0", 112};

int devNum = 0;


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/*Just to verify the name of device created before parsing aything.*/


{

if(optc == 'c')

{

printf("DEVICE name is %s\n", optarg);

if (strlen(optarg) > 10) {

/*check run-case 1*/

printf("Invalid device name\n");

exit(-1);

}

optind = 1;/*Reseting index to 1 again to start actual parsing*/

break;

}

}


{

switch(optc)

{

case 'c':

strncpy(dev.name, optarg, MAXLEN);

break;

case 'k':

devNum = atoi(optarg);


break;

case '?':

if (optopt == 'c' || optopt == 'k')

{

/*check run-case 3*/

printf("Option -%c requires an argument\n", optopt);

exit (-1);

}


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Anatomy of command line arguments in Linux http://mylinuxbook com/command-line-arguments-in-linux-part2/


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break;

default:


exit(0);

}

}




return 0;

}

./mkdevice -c ff123456789 -k 5

DEVICE name is ff123456789

Invalid device name

$ ./mkdevice -c okdev -k 15

DEVICE name is okdev

Device okdev created !

Device : okdev

Number : 15


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Anatomy of command line arguments in Linux http://mylinuxbook com/command-line-arguments-in-linux-part2/


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$ ./mkdevice -c okdev -k

DEVICE name is okdev

Option -k requires an argument

mycmd --display --file file.txt

ls --all

#include

int getopt_long(int argc, char * const argv[],

const char *optstring,

Anatomy of command line arguments in Linux http://mylinuxbook.com/command line arguments in linux part2/

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const struct option *longopts, int *longindex);

struct option

{

const char *name;

/* has_arg can't be an enum because some compilers complain about

type mismatches in all the code that assumes it is an int. */

int has_arg;

int *flag;

int val;

};

Anatomy of command line arguments in Linux http://mylinuxbook.com/command line arguments in linux part2/

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--create : create a device with name as argument

--number : device should have device number as provided argument.


#include

#include

#include

#include

#define MAXLEN 30

struct Device

{

char name[MAXLEN];

int number;

};


{

char optc = 0;

struct Device dev = {"dev_0", 112};struct option cmdLongOpts[] = {

{"create", required_argument, NULL, 'c'},

{"number", required_argument, NULL, 'k'},

{0, 0, 0, 0}

};

int devNum = 0;

while ((optc = getopt_long(argc, argv,"c:k:", cmdLongOpts, NULL)) != -1)

{

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switch(optc)

{

case 'c':

printf("Creating the device of name %s\n", optarg);

strncpy(dev.name, optarg, strlen(optarg));

break;

case 'k': devNum = atoi(optarg);


break;

default:


exit (0);

}

}




return 0;

}

$ gcc mkdevice.c -Wall -o mkdevice

$ ./mkdevice --create mlbdev



Device : mlbdev

Number : 112

$ ./mkdevice --create mlbdev --number 456

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Device : mlbdev

Number : 456

$ ./mkdevice --create mlbdev -k 321


Device mlbdev created !Device : mlbdev

Number : 321

optc = getopt_long(argc, argv,"c:k:W;", cmdLongOpts, NULL)

$ ./mkdevice -Wcreate mlbdev -k 321

$ ./mkdevice -Wcreate mlbdev -Wnumber 321

y g p y g p

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$ ls -l -t

$ mkdir --help

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Date post:	07-Aug-2018
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Anatomy of Command Line Arguments in Linux

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