Simple shell script problem

enigma87 · 10-04-2008, 03:28 AM

I'm having a problem with a shell script I've been writing this past hour. I'm trying to make a function that will simulate typing. The problem is that for small strings it does it really well, but not for longer strings. If anyone can take a look at my code and make suggestions as to how to make it as robust as possible, I'd be a million times grateful

Thanks guys!

Code:

### Start of typing function ###
echoType(){
text=$*
startnumber=0
number=$(echo $text | wc -c)
endnumber=$[ $number - 2 ]
#echo ${text:1:1}
#echo $text
#echo $endnumber

while [ $startnumber -le $endnumber ]; do
        echo -e "${text:$startnumber:1}\c"
        startnumber=$[ $startnumber + 1 ]
        sleep .05
done
echo
}
### End of typing function ###

   echoType "                     IDENTIFICATION NOT RECOGNIZED BY THE SYSTEM"
   echo
   echo
   echo
   echo
   echo
   echo
   echo
   echo
   echo
   echo
   echo
   echo
   echo
   echoType "                            ---CONNECTION TERMINATED---"

Mr. C. · 10-04-2008, 04:16 AM

The problem is that your white space gets lost in :

Code:

    number=$(echo $text | wc -c)

and is not counted by wc, so your string length is short. Use:

Code:

    number=$(echo "$text" | wc -c)

to quote the text so as not to loose your white space in your string.

colucix · 10-04-2008, 04:27 AM

An alternative:

Code:

number=${#text}
endnumber=$[ $number - 1 ]

the first gives the length of the string, including spaces. The second is modified, since the string does not contain the newline character appended by the echo command.

enigma87 · 10-04-2008, 12:26 PM

Thanks Mr. C, I dont know why I didnt try putting quotes around the $text. Also thanks colucix, learned another way of counting characters without needing to use wc

Thanks guys!

chrism01 · 10-05-2008, 07:47 PM

BTW, you can't sleep less than 1 second: http://www.ss64.com/bash/sleep.html

Mr. C. · 10-05-2008, 08:14 PM

Hey chrism01... actually, sleep can accept values < 1 second.

Code:

$ cat sleep
#!/bin/bash

sleep $1

$ strace -f ./sleep 2 2>&1 | grep nanosleep  
[pid  4609] nanosleep({2, 0}, NULL)     = 0

$ strace -f ./sleep .24 2>&1 | grep nanosleep  
[pid  4613] nanosleep({0, 240000000}, NULL) = 0

man nanosleep

Name
nanosleep - pause execution for a specified time
Synopsis
#define _POSIX_C_SOURCE 199309 #include <time.h>

int nanosleep(const struct timespec *req, struct timespec *rem);
Description
nanosleep() delays the execution of the program for at least the time specified in *req. The function can return earlier if a signal has been delivered to the process. In this case, it returns -1, sets errno to EINTR, and writes the remaining time into the structure pointed to by rem unless rem is NULL. The value of *rem can then be used to call nanosleep() again and complete the specified pause.

The structure timespec is used to specify intervals of time with nanosecond precision. It is specified in <time.h> and has the form

    struct timespec {
        time_t tv_sec;        /* seconds */
        long   tv_nsec;       /* nanoseconds */
    };

The value of the nanoseconds field must be in the range 0 to 999999999.

Try the posted app - it works.

colucix · 10-06-2008, 04:31 AM

Indeed, from the sleep man page

Quote:

Unlike most implementations that require NUMBER be an integer, here NUMBER
may be an arbitrary floating point number.

I think this new capability is tied to High Resolution Timers, which are supported
by the most recent kernels. See this post for some information about checking for
High Resolution Timers support into the installed kernel.

gnashley · 10-06-2008, 08:40 AM

You don't need a recent kernel to use fractional times with sleep. Perhaps a POSIX sleep can't do this.

colucix · 10-06-2008, 08:48 AM

I stand corrected.