STRING(3C) — HP-UX

NAME

strcat, strncat, strcmp, strncmp, strcpy, strncpy, strlen, strchr, strrchr, strpbrk, strspn, strcspn, strtok, nl_strcmp, nl_strncmp − character string operations

SYNOPSIS

#include <string.h>

char ∗strcat (s1, s2)
char ∗s1, ∗s2;

char ∗strncat (s1, s2, n)
char ∗s1, ∗s2;
int n;

int strcmp (s1, s2)
char ∗s1, ∗s2;

int strncmp (s1, s2, n)
char ∗s1, ∗s2;
int n;

char ∗strcpy (s1, s2)
char ∗s1, ∗s2;

char ∗strncpy (s1, s2, n)
char ∗s1, ∗s2;
int n;

int strlen (s)
char ∗s;

char ∗strchr (s, c)
char ∗s;
int c;

char ∗strrchr (s, c)
char ∗s;
int c;

char ∗strpbrk (s1, s2)
char ∗s1, ∗s2;

int strspn (s1, s2)
char ∗s1, ∗s2;

int strcspn (s1, s2)
char ∗s1, ∗s2;

char ∗strtok (s1, s2)
char ∗s1, ∗s2;

int nl_strcmp (s1, s2)
char ∗s1, ∗s2;

int nl_strncmp (s1, s2, n)
char ∗s1, ∗s2;
int n;

DESCRIPTION

The arguments s1, s2, and s point to strings (arrays of characters terminated by a null character). Character is defined as a 1-byte element of type unsigned char for all functions except nl_strcmp and nl_strncmp. For the functions nl_strcmp and nl_strncmp, the definition of a character has been extended and may be 1 or 2 bytes in length to accomodate languages with large character sets (see hpnls(5)). The functions strcat, strncat, strcpy, and strncpy all alter s1. These functions do not check for overflow of the array pointed to by s1.

Strcat appends a copy of string s2 to the end of string s1. Strncat appends a maximum of n characters. It copies fewer if s2 is shorter than n characters. Each returns a pointer to the null-terminated result (the original value of s1).

Strcmp compares its arguments and returns an integer less than, equal to, or greater than zero, depending on whether s1 is lexicographically less than, equal to, or greater than s2. (NULL values for s1 and s2 are treated the same as pointers to null strings.) Strncmp makes the same comparison but looks at a maximum of n characters (n less than or equal to zero yields equality).

Strcpy copies string s2 to s1, stopping after the null character has been copied. Strncpy copies exactly n characters, truncating s2 or adding null characters to s1 if necessary. The result will not be null-terminated if the length of s2 is n or more. Each function returns s1. Note that strncpy should not be used to copy n bytes of an arbitrary structure. If that structure contains a null byte anywhere, strncpy will terminate the copy when it encounters the null byte, thus returning fewer than n bytes.

Strlen returns the number of characters in s, not including the terminating null character.

Strchr (strrchr) returns a pointer to the first (last) occurrence of character c in string s, or a NULL pointer if c does not occur in the string. The null character terminating a string is considered to be part of the string.

Strpbrk returns a pointer to the first occurrence in string s1 of any character from string s2, or a NULL pointer if no character from s2 exists in s1.

Strspn (strcspn) returns the length of the initial segment of string s1, which consists entirely of characters from (not from) string s2.

Strtok considers the string s1 to consist of a sequence of zero or more text tokens separated by spans of one or more characters from the separator string s2. The first call (with pointer s1 specified) returns a pointer to the first character of the first token, and will have written a null character into s1 immediately following the returned token. The function keeps track of its position in the string between separate calls, so that subsequent calls (which must be made with the first argument a NULL pointer) will work through the string s1 immediately following that token. In this way subsequent calls will work through the string s1 until no tokens remain. The separator string s2 may be different from call to call. When no token remains in s1, a NULL pointer is returned.

Nl_strcmp compares arguments s1 and s2 that point to strings (arrays of characters, possibly multi-byte, terminated by a null character), using language-dependent collating information. An integer greater than, equal to, or less than zero is returned, depending on whether s1 is greater than, equal to, or less than s2. NULL values for s1 and s2 are treated like pointers to null strings. Nl_strncmp makes the same comparisons as nl_strcmp, but looks at a maximum of n characters (n less than or equal to zero yields equality). Nl_strcmp and nl_strncmp perform their operations based upon the loaded NLS environment (see nl_init(3C)).

Nl_strcmp and nl_strncmp, used by sort(1), provide a full “dictionary” or “context based” language-dependent comparison incorporating the following collation features:

Two_to_one conversions
Some languages, such as Spanish, require two adjacent characters to occupy one position in the collating sequence. Examples are “CH” (which follows “C”) and “LL” (which follows “L”).

One_to_two conversions
Some languages, such as German, require one character (for example, “sharp S”) to occupy two adjacent positions in the collating sequence.

Don’t care characters
Some languages designate certain characters to be ignored in character comparisons. For example, if “−” is a “don’t care” character, the strings “REACT” and “RE−ACT” would equal each other when compared.

Case and accent priority
Many languages require a “two-pass” collating algorithm. In the first pass, accents are stripped off letters and the resulting two strings are compared; if they are equal, a second pass with the accents reinserted is performed to break the tie. The case of letters can also be first ignored and then used to break ties in this fashion.

For user convenience, all these functions are declared in the optional <string.h> header file.

WARNINGS

The copy operations cannot check for overflow of any receiving string. NULL destinations cause errors. NULL sources are treated as zero-length strings.

Character movement is performed differently in different implementations. Thus overlapping moves may yield surprises.

DEPENDENCIES

Series 500
Nl_strcmp and nl_strncmp are currently not supported. Use routines described in nl_string(3C) instead.

AUTHOR

String was developed by AT&T and HP.

Museum

Related Articles