Working with the Unix OS

C Libraries
}
while (!feof(fp1))
putc(getc(fp1),fp2);
fclose(fp1);
fclose(fp2);
return SUCCESS;
Unbuffered I/O
standard device | file descriptor
stdin 0
stdout 1
stderr 2
void close(int fd)
int creat(char *name, int perms)
long Lseek(int fd, long offset, int origin);
int open(char *name, int flags, int perms)
int read(int fd, char *buf, int n)
int write(int fd, char *buf, int n)
unlink(char *name)
flags
O_RDONLY
O_WRONLY
O_RDWR
open read only
open write only
open read & write
perms
0666 all read & write
String Operations
#include
/* s and t are char * and c and n are int */
strcat(s,t) concatenate t to end of s
strncat(s,t,n) concatenate n characters of t to end of s
strcmp(s,t) return -ve if st
strncmp(s,t,n) same as strcmp but only in first n chars
strcpy(s,t) copy t to s
strncpy(s,t,n) copy n characters from t to s
strlen(s) return length of s
strchr(s,c) return pointer to first c in s
strrchr(s,c) return pointer to last c in s
Testing and Conversion
#include
/* function returns int and c is int */
isalpha(c) non-zero if c is alphabetic
isupper(c) non-zero if c is upper case
islower(c) non-zero if c is lower case
isdigit(c) non-zero if c is digit
isalnum(c) non-zero if isalpha(c) or isdigit(c)
isspace(c) non-zero if c is blank, tab, lf, cr, ff, vt
toupper(c) return c converted to upper case
tolower(c) return c converted to lower case
Error handling – Stderr and Exit
Output which is sent to stderr goes to the screen not down a pipeline or into an output file. Exit stops the program
and returns a value back to the system.
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