scanf() has an unfortunate problem where, if it finds any bad data in the stream, it puts it back. You are asking for %d, so it looks for digits. If it sees any non-digits, it will give up and not even show them to you.
Imagine you're trying to read 9 numbers with 9 scanf calls, and on the very first one you type in A then enter. The first scanf will see 'A', decide it's not a number, and put it back. This means the second will also see 'A'. So will the third, fourth, fifth, sixth, seventh, eighth, and ninth.
sscanf, which operates on strings instead of streams, avoids this problem, since it has nowhere to "put back" the letter into. It just uses the string you give it and doesn't care what happened last time. fgets() and sscanf() make a good team; fgets reads entire lines and turns them into strings, while sscanf() processes strings and turns them into what you want.
Note that this will accept things like 1234a, since sscanf will stop at the a.
Last edited by Corona688; 01-04-2013 at 02:18 PM..
These 2 Users Gave Thanks to Corona688 For This Post:
Hi,
First off I usually script in the bash shell.
Ok, in my script I am checking to see if the filename has a .txt extension.
So I was trying:
if
then
echo "Must contain a valid .txt extension"
fiandif ]
then
echo "Must contain a valid .txt extension"
fiBut no go the first... (5 Replies)
Correct me if i'm wrong, but by adding "#!/bin/ksh" at the start of a script will force it to run in the korn shell no matter which shell you are currently using?? (2 Replies)
I'm using solaris and i have an old script that an ex employee wrote but i can't seem to get it working. well is just one part of the script
if ($?MC_PROD_DIR == 0) setenv MC_PROD_DIR $HOME/PRODUCTION
source $MC_PROD_DIR/scripts/localenv
** i understand what this part of the script is... (1 Reply)
Can anyone help with these scripts? Im new to this and struggling. Thank you for your help.
Pre-requisites
Create a file with x amount of lines in it, the content of your choice. (Have already done this)
Script 1
Write a script that takes two arguments. The first being a line of text,... (3 Replies)
Anyone know why this won't work?
#!/usr/bin/ksh
for db in `cat /etc/oratab|egrep ':N|:Y' | grep -v \* | cut -f1 -d":"`
do
echo "************************"
echo "database is $db"
echo "************************"
done
I am getting an error on the line... (7 Replies)
Here is my problem.
I have a txt file with a list of user names in both upper case and lower case. I need to remove the names from the passwd file. I want to be able to run a script that looks at my txt list and then removes those names from the passwd file. It would be nice if it backed up the... (3 Replies)
I am trying to write a script to check the STIG our unix boxes. I want to put in checks to determine if certain files or directories are there. For example:
If /opt/SUNWexplo exists
echo "Sun Explorer exists"
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I am sure I could write... (2 Replies)
I have a script that will calculate some information about the current directory that I run the script in. How can I have it where it gets an argument from the user(such as a directory) and the script calculate the information for the given directory? Any help is greatly appreciated. (8 Replies)
How can I include a counter in this if statement so only sends out 5 notifications.
# the if statement will check for the lines status, if status is down sends email
if
then
LIST="user@email.com"
mail -s "rje_lines_down" $LIST < ${tmpfile} #sends an email to list
fi
thanks... (2 Replies)
I know some tricks like this : echo " E"; sleep 0.1; clear;
echo " Er"; sleep 0.1; clear;
echo " Err"; sleep 0.1; clear;
echo " Erro"; sleep 0.1; clear;
echo " Error ";... (2 Replies)
Discussion started by: hakermania
2 Replies
LEARN ABOUT BSD
stdio
STDIO(3S)STDIO(3S)NAME
stdio - standard buffered input/output package
SYNOPSIS
#include <stdio.h>
FILE *stdin;
FILE *stdout;
FILE *stderr;
DESCRIPTION
The functions described in section 3S constitute a user-level buffering scheme. The in-line macros getc and putc(3S) handle characters
quickly. The higher level routines gets, fgets, scanf, fscanf, fread, puts, fputs, printf, fprintf, fwrite all use getc and putc; they can
be freely intermixed.
A file with associated buffering is called a stream, and is declared to be a pointer to a defined type FILE. Fopen(3S) creates certain
descriptive data for a stream and returns a pointer to designate the stream in all further transactions. There are three normally open
streams with constant pointers declared in the include file and associated with the standard open files:
stdin standard input file
stdout standard output file
stderr standard error file
A constant `pointer' NULL(0) designates no stream at all.
An integer constant EOF (-1) is returned upon end of file or error by integer functions that deal with streams.
Any routine that uses the standard input/output package must include the header file <stdio.h> of pertinent macro definitions. The func-
tions and constants mentioned in sections labeled 3S are declared in the include file and need no further declaration. The constants, and
the following `functions' are implemented as macros; redeclaration of these names is perilous: getc, getchar, putc, putchar, feof, ferror,
fileno.
SEE ALSO open(2), close(2), read(2), write(2), fread(3S), fseek(3S), f*(3S)
DIAGNOSTICS
The value EOF is returned uniformly to indicate that a FILE pointer has not been initialized with fopen, input (output) has been attempted
on an output (input) stream, or a FILE pointer designates corrupt or otherwise unintelligible FILE data.
For purposes of efficiency, this implementation of the standard library has been changed to line buffer output to a terminal by default and
attempts to do this transparently by flushing the output whenever a read(2) from the standard input is necessary. This is almost always
transparent, but may cause confusion or malfunctioning of programs which use standard i/o routines but use read(2) themselves to read from
the standard input.
In cases where a large amount of computation is done after printing part of a line on an output terminal, it is necessary to fflush(3S) the
standard output before going off and computing so that the output will appear.
BUGS
The standard buffered functions do not interact well with certain other library and system functions, especially vfork and abort.
LIST OF FUNCTIONS
Name Appears on Page Description
clearerr ferror.3s stream status inquiries
fclose fclose.3s close or flush a stream
fdopen fopen.3s open a stream
feof ferror.3s stream status inquiries
ferror ferror.3s stream status inquiries
fflush fclose.3s close or flush a stream
fgetc getc.3s get character or word from stream
fgets gets.3s get a string from a stream
fileno ferror.3s stream status inquiries
fopen fopen.3s open a stream
fprintf printf.3s formatted output conversion
fputc putc.3s put character or word on a stream
fputs puts.3s put a string on a stream
fread fread.3s buffered binary input/output
freopen fopen.3s open a stream
fscanf scanf.3s formatted input conversion
fseek fseek.3s reposition a stream
ftell fseek.3s reposition a stream
fwrite fread.3s buffered binary input/output
getc getc.3s get character or word from stream
getchar getc.3s get character or word from stream
gets gets.3s get a string from a stream
getw getc.3s get character or word from stream
printf printf.3s formatted output conversion
putc putc.3s put character or word on a stream
putchar putc.3s put character or word on a stream
puts puts.3s put a string on a stream
putw putc.3s put character or word on a stream
rewind fseek.3s reposition a stream
scanf scanf.3s formatted input conversion
setbuf setbuf.3s assign buffering to a stream
setbuffer setbuf.3s assign buffering to a stream
setlinebuf setbuf.3s assign buffering to a stream
sprintf printf.3s formatted output conversion
sscanf scanf.3s formatted input conversion
ungetc ungetc.3s push character back into input stream
4th Berkeley Distribution May 13, 1986 STDIO(3S)