CSE2031 Lecture 10

Specifier	Field type	Converted using	Arg is pointer to
d	Integer (optionally signed)	Strtol with base 10	Int
hd	''	''	Short int
ld	''	''	Long int
I	''	Strtol with base = 0 Reads 045 as octal Ox92 as hexadecimal
hi			Short
li	''	''	Long
O	Integer	Strtoul base 8	Unsigned int
ho	''	''	Unsigned short
Lo	''	''	Unsigned long
U	''	Base 10	''
Hu	''	''	''
Lu	''	''	''
X	Integer	Strtoul base 16 Does not accept AB	Unsigned int
Hx	''	''	''
Lx	''	''	''
E	Floating point input field	Strtol	Float
le	''	''	Double
Le	''	''	Long double

 

 

fscanf

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#include <stdio.h>

int fscanf(FILE*stream, const char * format, ...)

scanf is like fscanf(stdin,...)

sscanf(const char* src, ...format...

return value = # of text fields converted to values that are stored

scanf("%d %f", &n,&x)

return EOF if the function stops scanning

because the attempt to get next character it sets end of file or error indicator

for stream ferror(fp), feof(fp)

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format string

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can have white space

matches any amount of whitespace in the input

"%d<>%f

<> represents a space

literal text

scan conversion specifier

    -like those from printf ( sort of )

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conversion specifier

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-start w/ % sign

-*assignment supression

    looks like scanf(%d %*d %d &m)

-w field width

-conversion specifier

    -give type of argument to expect

        -always a pointer to something

    -how to determind conversion field

    -how to convert value to store

    

(a) scan set

[ ]

keep reading any of these characters (above)

{^ }

Don't read these characters (above)

b) otherwise (and usually)

    d

    i

    o    hl

    u

    x

    X

d and i are different in scan f

 

    eE

    fF    lL

    gG

 

    c

    s

    n

    p

 

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%wc    w chars no '\0' appended        store arg char*

defaults to 1 for %c

 

%ws    w chars                charx then append '\0'

default %s all of next token

 

scanf("%10c", buf)             reads first 10 chars even if it is whitespace

scanf("%10s", buf)            skips all the whitespace reads first 10 chars

 

char *p;

strtol(" 347atx ", &p, 6);

//skips whitespace and reads legal digits in 'this' base (this being 6)

//returns 22 (3 sixes + 4) and pointer p points to the 7

if value outside the range it will return LONG_MAX/ LONG_MIN + set errno to ERANGE

0 <-- system call

-1

x

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file* <--Fopen

NULL

x

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perror("usermessage");            prints out "usermessage: system error messsage" error message corresponding to error number

strerror(errno)                 returns appropriate error string