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From: Orlando Sotomayor-Diaz (The Moderator) <cbosgd!std-c>


mod.std.c Digest            Thu, 15 May 86       Volume 16 : Issue  17

Today's Topics:
         MORE C standard differences Apr85-Feb86, part 7 of 9
----------------------------------------------------------------------

Date: 
From: ihnp4!utzoo!lsuc!msb
Subject: MORE C standard differences Apr85-Feb86, part 7 of 9
To: utzoo!ihnp4!hou2d!osd

# D.11.3.1 The strcat function

       The strcat function appends a copy of the string pointed to by s2
  *    {-->  (including  the  terminating null character)} to the end of
       the string pointed to by s1.



# D.11.3.2 The strncat function

       The strncat function appends not more than n  characters  of  the
  *    string  pointed to by s2 {--> (not including the terminating null
       character)} to the end of the string pointed to by s1.



# D.11.3.2 The strncat function

N-->   The number of characters that may end up in the array pointed  to
N-->   by s1 is strlen(s1)+n+1.

N-->   Forward references: the strlen function (#D.11.6.3).



# D.11.4 {Length and -->} Comparison functions



# D.11.4.1 The memcmp function

N-->   The contents of "holes" used as padding for purposes of alignment
N-->   within  structure  objects are indeterminate, unless the contents
N-->   of the entire object have been set explicitly by  the  calloc  or
N-->   memset function.  Unions and strings shorter than their allocated
N-->   space may also cause problems in comparison.



# D.11.5.1 The memchr function

  *    The memchr function locates the first occurrence of c {-->  (con-
       verted  to  an unsigned char)} in the initial n characters of the
       object pointed to by s.



# D.11.5.2 The strchr function

  *    The strchr function locates the first occurrence of c {-->  (con-
       verted to a char)} in the string pointed to by s.

Remark: And the same change for strrchr (#D.11.5.5).



# {--> D.11.5.7 The strstr function}

N-->   Synopsis

N-->               #include <string.h>
N-->               char *strstr(const char *s1, const char *s2);

N-->   Description

N-->   The strstr function locates the first occurrence  of  the  string
N-->   pointed to by s2 in the string pointed to by s1.

N-->   Returns

N-->   The strstr function returns a pointer to the located string, or a
N-->   null pointer if the string is not found.



# {D.11.5.7 --> D.11.5.8} The strtok function

<--O   The strtok function considers the string pointed to by s1 to con-
<--O   sist of a sequence of zero or more text tokens separated by spans
<--O   of one or more characters from the string pointed to by s2.

N-->   A sequence of calls to the  strtok  function  breaks  the  string
N-->   pointed to by s1 into a sequence of tokens, each of which is del-
N-->   imited by a character from the string  pointed  to  by  s2.   The
N-->   first  call  in the sequence has s1 as its first argument, and is
N-->   followed by calls with a null pointer as their first argument.

       The separator string pointed to by s2 may be different from  call
       to call.

N-->   The first call in the sequence searches s1 for the first  charac-
N-->   ter that is NOT contained in the current separator string s2.  If
N-->   no such character is found, there are no tokens in  s1,  and  the
N-->   strtok  function  returns a null pointer.  If such a character is
N-->   found, it is the start of the first token.

N-->   The strtok function then searches from there for a character that
N-->   IS contained in the current separator string.  If no such charac-
N-->   ter is found, the current token extends to the end of the  string
N-->   pointed  to by s1, and subsequent searches for a token will fail.
N-->   If such a character is found, it is overwritten by a null charac-
N-->   ter,  which  terminates  the  current token.  The strtok function
N-->   saves a pointer to the following character, from which  the  next
N-->   search for a token will start.

N-->   Each subsequent call, with a null pointer as  the  value  of  the
N-->   first  argument,  starts  searching  from  the  saved pointer and
N-->   behaves as described above.

<--O   The first call to the strtok function returns a  pointer  to  the
<--O   initial character of the first token, and will have written a NUL
<--O   character into s1 immediately following the returned token.  Each
<--O   subsequent  call  (with the value of the first argument null) re-
<--O   turns a pointer to a subsequent token.  When no token remains  in
<--O   s1, the strtok function returns a null pointer.

N-->   The strtok function returns a pointer to the first character of a
N-->   token, or a null pointer if there is no token.



# {D.11.5.7 --> D.11.5.8} The strtok function

N-->   Example

N-->         #include <string.h>
N-->         static char str[] = "?a???b,,,#c";
N-->         char *t;

N-->         t = strtok(str, "?");   /* t points to the token "a" */
N-->         t = strtok(NULL, ",");  /* t points to the token "??b" */
N-->         t = strtok(NULL, "#,"); /* t points to the token "c" */
N-->         t = strtok(NULL, "?");  /* t is a null pointer */



# {--> D.11.6 Miscellaneous functions}



# {D.11.2.2 --> D.11.6.1} The memset function

  *    The memset function copies the value of c ({cast  -->  converted}
  *    to  an unsigned char) into each of the first n {bytes --> charac-
       ters} of the object pointed to by s.



# {--> D.11.6.2 The strerror function}

N-->   Synopsis

N-->               #include <string.h>
N-->               char *strerror(int errnum);

N-->   Description

N-->   The strerror function maps the error number in errnum to an error
N-->   message string.

N-->   Returns

N-->   The strerror function returns a pointer to the string,  the  con-
N-->   tents  of which are implementation-defined.  The array pointed to
N-->   is not modifiable by the program, but may  be  overwritten  by  a
N-->   subsequent call to the strerror function.



# {D.11.4.3 --> D.11.6.3} the strlen function

       The strlen function computes the length of the string pointed  to
  *    by s {, not counting the terminating NUL character -->}.  ...

  *    The strlen function returns the number of {initial  -->}  charac-
  *    ters {--> that precede the terminating null character}.



# D.12.1 Components of time

       Many functions deal with a "calendar time"  that  represents  the
  *    current  date  {-->  (according  to  the Gregorian calendar)} and
       time.



# D.12.1 Components of time

  *                int tm_mon;    /* {month of the year -->
                         months since January} - [0, 11] */

       ...
  *                int tm_yday;   /* {day of the year -->
                         days since January 1} - [0, 365] */

------------------------------

End of mod.std.c Digest - Thu, 15 May 86 13:32:04 EDT
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