|
Pages: [1]
|
  |
|
|
Author
|
Topic: *nix command line args (Read 95 times)
|
|
Guardian_Tenshi
Global Moderator
Karma: +53/-26
 Offline
Gender: 
Posts: 1114
    
  
|
 |
*nix command line args
« on: March 19, 2004, 10:05:40 PM »
|
|
Ok, so our assignment is to write a c-shell script file, and not a very complex one...but there is one thing that is still alluding me. She wants to pass it arguments. For example, in this assigment, she wants it to be called "timer" and then timer is called:
% timer 9000
the script would then do a simple conversion and convert 9000 seconds into 2 hours and 30 minutes. However, we aren't allowed to use anything but integers. So...I understand how to validate the number of args, I understand how to prompt the user should he/she not provide enough args...what I DON'T understand, is the logic to prove if the number is a valid integer. That means it can't be a float, double, or string...think someone can help?? <<looks at porter, slight, and terraji>>
Tenshi
|
|
 Logged
|
|
|
|
Grounded
Admin Team
CSR Connoisseur
Karma: +158/-21
Offline
Posts: 3176
|
|
Re:*nix command line args
« Reply #1 on: March 20, 2004, 04:33:39 AM »
|
|
Do you have commands that let you do modulo arithmetic? I'm guessing you do, in which case the number would be valid if it is equal to 0 mod 30 (assuming you're only supposed to convert if the number is a multiple of 30 - you could go to 15 for quarter hours).
|
|
Logged
|
|
|
|
Terraji
Admin Team
CSR Connoisseur
Karma: +35/-15
Offline
Gender:
Posts: 789
|
|
Re:*nix command line args
« Reply #2 on: March 20, 2004, 01:25:21 PM »
|
|
It is my understanding that args always show up in your C program as strings.
To validate whether it is not a word, float or double etc, you could scan through the arg string once and make sure that each char is between 48 and 57 (ascii 0-9) when you cast them to an int. If there is a period (decimal place) or a letter the string would be rejected. Once you have a verified string you can use the | int atoi(const char * nptr); |
|
function to convert it to a integer. I dont think you have to include a special library to use the atoi function, if not, it is probably in the string.h standard library.
One thing to watch out for which has messed me up countless times, is that for the last command line arg, it includes the newline character from when you pressed enter to execute the program on the command line. For example, %timer 9000 would have arg[1] string as ['9','0','0','0','\n',null]
I hope this helps
Terraji
|
|
Logged
|
|
|
|
Guardian_Tenshi
Global Moderator
Karma: +53/-26
Offline
Gender:
Posts: 1114
|
|
Re:*nix command line args
« Reply #3 on: March 20, 2004, 04:34:40 PM »
|
|
no, no, a C-shell script....not a c++ pgm....
if (#$argv == 0) then
# run code here to prompt user for seconds.
else if (#$argv == 1) then
# this implies $1 == input value in seconds.
# then grounded is kinda right...but I have to use a combination of integer division, and modulo to convert...
@seconds = $1 / 60
@temp = $1 % 60
# etc, etc, etc....
|
|
the problem is I need conditions to make sure that $1 is indeed an integer value, and not some random garbage...
I could call the function:
% timer 9032
or:
% timer five
technically five is still one arg, and therefore, would work with the code I have, but unix unlike c++ will not turn 'five' into a numerical value based on ascii characters...so I need to damn near grep through it looking for '^[0-9]+'
but how i can imbed that in my code beats the hell out of me...
Tenshi
|
|
Logged
|
|
|
|
Terraji
Admin Team
CSR Connoisseur
Karma: +35/-15
Offline
Gender:
Posts: 789
|
|
Re:*nix command line args
« Reply #4 on: March 20, 2004, 05:30:53 PM »
|
|
Okay, then it is out of my area of expertise 
I'm gonna have a peek in a textbook that I own that I think relates. At the very least, it might help me learn something about c shell scripts.
|
|
Logged
|
|
|
|
Porter
[Wumpa]
Board Admin
Karma: +176/--88
Offline
Gender:
Posts: 3910
|
|
Re:*nix command line args
« Reply #5 on: March 22, 2004, 01:51:13 PM »
|
|
I hate it when you're forced to use tools that aren't designed to do what you've been asked to do. Much less c-shell! VERY unfriendly. Shell scripts should pretty much always be bash based. Plus, perl could do this entire assignment in ~4 lines of code.
What really gets me is that poor Tenshi is being TAUGHT bad practices.... instead of picking them up on his own like any programmer worth his salt. 
Sorry tenshi, I don't know shell scripting well enough to be able to help. And of course, since I've been away for a while, I'm probably too late to help anyway.
|
|
Logged
|
[Wumpa] Porter
--Silent, professional, lethal... sometimes.
|
|
|
slightcrazed
-TWB-
Admin Team
CSR Connoisseur
Karma: +65/-7
Offline
Gender:
Posts: 983
|
|
Re:*nix command line args
« Reply #6 on: March 22, 2004, 03:01:46 PM »
|
|
Shell scripts should pretty much always be bash based.
|
|
Agreed. c-shell is quickly becoming outdated, if it isn't already there.
Plus, perl could do this entire assignment in ~4 lines of code.
|
|
So could python and half a dozen other languages. I could probably bang out a bash script that was about 10 lines, which isn't to shabby for a command line language.
| What really gets me is that poor Tenshi is being TAUGHT bad practices.... instead of picking them up on his own like any programmer worth his salt. |
|
So true. Programming is a language in and of itself, and there is a right way, and a wrong way to do thing. "Me go store" might get the point across, but "I am going to go to the store" is much more properer. (play on words  )
I'm not sure if bash includes the ability to test for input type (I believe it does), but you might be able to fudge it by testing the value against a multiplier. If 'var1' is your input variable, then multiply it by 1, and if it is text you will get a 'null' response. If it is numerical then you can grep it for a '.' and if one is found, then you can yell at the user to use whole numbers only.
It's ugly, but it would probably work. I'm going from memory, I'd have to check the bash scripting guide to be more help.
Which reminds me, do a google for 'bash scripting guide' and you should get about 50,000 hits for it. Probably the best reference there is out there.
Then you just need to spend a couple days convincing your teacher to let you use bash, instead of c-shell.
She sells c-shells by the sea shore.
slight
|
|
Logged
|
I once beat Drizzt Do'Urden at thumb wrestling.
|
|
|
Guardian_Tenshi
Global Moderator
Karma: +53/-26
Offline
Gender:
Posts: 1114
|
|
Re:*nix command line args
« Reply #7 on: March 22, 2004, 07:17:08 PM »
|
|
Well, alot of help you guys are but thankfully slight was right about looking on the internet, i was reading some stuff, about egrep and figured it out. I'm not sure this is the BEST way, but this way works...
...
...
echo "$1" | egrep '^[0-9]+$' >& /dev/null
if ($status == 0) then
...
...
...
...
|
|
Thanks for the help though guys. Surprisingly, this time I think I stumped Porter. yay!! for me...
Tenshi
|
|
Logged
|
|
|
|
Guardian_Tenshi
Global Moderator
Karma: +53/-26
Offline
Gender:
Posts: 1114
|
|
Re:*nix command line args
« Reply #8 on: March 23, 2004, 11:56:47 PM »
|
|
#!/bin/csh
# this program will takes one integer argument in seconds
# it will convert the num of seconds to secs, mins, hrs, days.
# This program is written by John A. Lillard
# Number of Argument Validation
if ($#argv == 0) then
echo -n "Please enter an integer value in seconds: "
set initval = $<
# initval should be an int, but will be checked later.
else if ($#argv > 1) then
echo "Invalid number of arguments for $0"
echo "Usage: $0 [int seconds]"
exit 1
else
set initval = $1
# initval should be an int, but will be checked later.
endif
# Is the argument an integer value??
echo "$initval" | egrep '^[0-9]+$' >& /dev/null
if ($status == 0) then
# math to do conversion below...
@ days = $initval / 86400
@ temp1 = $initval % 86400
@ hours = $temp1 / 3600
@ temp2 = $temp1 % 3600
@ minutes = $temp2 / 60
@ seconds = $temp2 % 60
else
echo "Invalid argument given"
echo "Usage: $0 [int seconds]"
exit 1
endif
# Begin Printing Data...
if ($seconds == 1) then
echo "1 second"
else if ($seconds != 0) then
echo "$seconds seconds"
endif
if ($minutes == 1) then
echo "1 minute"
else if ($minutes != 0) then
echo "$minutes minutes"
endif
if ($hours == 1) then
echo "1 hour"
else if ($hours != 0) then
echo "$hours hours"
endif
if ($days == 1) then
echo "1 day"
else if ($days != 0) then
echo "$days days"
endif
exit 0
|
|
|
|
Logged
|
|
|
|
slightcrazed
-TWB-
Admin Team
CSR Connoisseur
Karma: +65/-7
Offline
Gender:
Posts: 983
|
|
Re:*nix command line args
« Reply #9 on: March 24, 2004, 07:29:06 AM »
|
|
Looks good, although I think you might have been able to work in some simpler code using a case statement, as opposed to all the if statements at the end. Looks good none-the-less.
slight
|
|
Logged
|
I once beat Drizzt Do'Urden at thumb wrestling.
|
|
|
|
Pages: [1]
|
|
|
|
|
|
CSReloaded Forums | Powered by YaBB SE
© 2001-2003, YaBB SE Dev Team. All Rights Reserved. |
|
|
