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C_library_functions.md

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C Library Functions

/usr/include/string.h

Memory functions

Here source and destination are memory addresses.

  • memmem : find the first occurrence of NEEDLE in HAYSTACK.
  • memcpy : copy N bytes of SRC to DEST
  • memccpy : Copy no more than N bytes of SRC to DEST, stopping when C is found. Return the position in DEST one byte past where C was copied, or NULL if C was not found in the first N bytes of SRC.
  • memmove : copy N bytes of SRC to DEST, guaranteeing correct behavior for overlapping strings.
  • memset : set N bytes of S to C.
  • memcmp : compare N bytes of S1 and S2.
  • memchr : search N bytes of S for C.
  • memrchr : search N bytes of S for the final occurence of C.
  • rawmemchr : search in S for C. This is similar to memchr but there is no length limit.

String functions

Here source and destination are strings (array of characters terminated by a NULL byte).

  • strnlen : find the length of STRING, but scan at most MAXLEN characters. If no '\0' terminator is found in that many characters, return MAXLEN.

  • strncpy : copy no more than N chars of SRC to DEST.

  • strncat : Append no more than N characters from SRC onto DEST.

  • strncmp : compare N characters of S1 and S2.

  • strcoll : compare the collated forms of S1 and S2.

  • strxfrm : put a transformation of SRC into no more than N bytes of DEST.

  • strcoll_l : compare the collated forms of S1 and S2, using sorting rules from L (locale).

  • strxfrm_l : put a transformation of SRC into no more than N bytes of DEST, using sorting rules from L.

  • strndup : return a malloc'd copy of at most N bytes of STRING. The resultant string is terminated even if no NULL terminator appears before STRING[N].

  • strndupa : return an alloca'd copy of at most N bytes of string.

  • strchr : find the first occurence of C in S.

  • strrchr : find the last occurence of C in S.

  • strchrnul : it is similar to strchr. But it returns a pointer to the closing NULL byte in case C is not found in S.

  • strspn : return the length of the initial segment of S which consists entirely of characters in ACCEPT.

  • strcspn : return the length of the initial segment of S which consists entirely of characters not in REJECT.

  • strpbrk : find the first occurrence in S of any character in ACCEPT.

  • strstr : find the first occurrence of NEEDLE in HAYSTACK.

  • strcasestr: similar to strstr but this function ignores the case of both strings.

  • strtok : divide S into tokens separated by characters in DELIM.

  • strerror : return a string describing the meaning of the errno code in ERRNUM parameter.

  • strsignal : return a string describing the meaning of the signal number in SIG.

  • basename : return the file name within directory of FILENAME.

  • explicit_bzero : set N bytes of S to 0.

  • strsep : return the next DELIM-delimited token from *STRINGP

  • strverscmp : compare S1 and S2 as strings holding name & indices/version numbers.

  • strfry : Sautee STRING briskly.

  • memfrob : Frobnicate N bytes of S.

Degraded Functions
* strcpy    : copy SRC to DEST
* strcat    : Append SRC onto DEST. 
* strcmp    : compare S1 and S2.  
* strdup    : duplicate S, returning an identical malloc'd string.  
* strdupa   : Duplicate S, returning an identical alloca'd string (memory on stack segment).  
* strlen    : return the length of S.