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/*
* Many systems have putenv() but no setenv(). Other systems have setenv()
* but no putenv() (MIPS). Still other systems have neither (NeXT). This is a
* re-implementation that hopefully ends all problems.
*
* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
*/
#ifndef lint
static char sccsid[] = "@(#) environ.c 1.2 94/03/23 16:09:46";
#endif
/* System libraries. */
extern char **environ;
extern char *strchr();
extern char *strcpy();
extern char *strncpy();
extern char *malloc();
extern char *realloc();
extern int strncmp();
extern void free();
#ifdef no_memcpy
#define memcpy(d,s,l) bcopy(s,d,l)
#else
extern char *memcpy();
#endif
/* Local stuff. */
static int addenv(); /* append entry to environment */
static int allocated = 0; /* environ is, or is not, allocated */
#define DO_CLOBBER 1
/* namelength - determine length of name in "name=whatever" */
static int namelength(name)
char *name;
{
char *equal;
equal = strchr(name, '=');
return ((equal == 0) ? strlen(name) : (equal - name));
}
/* findenv - given name, locate name=value */
static char **findenv(name, len)
char *name;
int len;
{
char **envp;
for (envp = environ; envp && *envp; envp++)
if (strncmp(name, *envp, len) == 0 && (*envp)[len] == '=')
return (envp);
return (0);
}
/* getenv - given name, locate value */
char *getenv(name)
char *name;
{
int len = namelength(name);
char **envp = findenv(name, len);
return (envp ? *envp + len + 1 : 0);
}
/* putenv - update or append environment (name,value) pair */
int putenv(nameval)
char *nameval;
{
char *equal = strchr(nameval, '=');
char *value = (equal ? equal : "");
return (setenv(nameval, value, DO_CLOBBER));
}
/* unsetenv - remove variable from environment */
void unsetenv(name)
char *name;
{
char **envp;
if ((envp = findenv(name, namelength(name))) != 0)
while (envp[0] = envp[1])
envp++;
}
/* setenv - update or append environment (name,value) pair */
int setenv(name, value, clobber)
char *name;
char *value;
int clobber;
{
char *destination;
char **envp;
int l_name; /* length of name part */
int l_nameval; /* length of name=value */
/* Permit name= and =value. */
l_name = namelength(name);
envp = findenv(name, l_name);
if (envp != 0 && clobber == 0)
return (0);
if (*value == '=')
value++;
l_nameval = l_name + strlen(value) + 1;
/*
* Use available memory if the old value is long enough. Never free an
* old name=value entry because it may not be allocated.
*/
destination = (envp != 0 && strlen(*envp) >= l_nameval) ?
*envp : malloc(l_nameval + 1);
if (destination == 0)
return (-1);
strncpy(destination, name, l_name);
destination[l_name] = '=';
strcpy(destination + l_name + 1, value);
return ((envp == 0) ? addenv(destination) : (*envp = destination, 0));
}
/* cmalloc - malloc and copy block of memory */
static char *cmalloc(new_len, old, old_len)
char *old;
int old_len;
{
char *new = malloc(new_len);
if (new != 0)
memcpy(new, old, old_len);
return (new);
}
/* addenv - append environment entry */
static int addenv(nameval)
char *nameval;
{
char **envp;
int n_used; /* number of environment entries */
int l_used; /* bytes used excl. terminator */
int l_need; /* bytes needed incl. terminator */
for (envp = environ; envp && *envp; envp++)
/* void */ ;
n_used = envp - environ;
l_used = n_used * sizeof(*envp);
l_need = l_used + 2 * sizeof(*envp);
envp = allocated ?
(char **) realloc((char *) environ, l_need) :
(char **) cmalloc(l_need, (char *) environ, l_used);
if (envp == 0) {
return (-1);
} else {
allocated = 1;
environ = envp;
environ[n_used++] = nameval; /* add new entry */
environ[n_used] = 0; /* terminate list */
return (0);
}
}
#ifdef TEST
/*
* Stand-alone program for test purposes.
*/
/* printenv - display environment */
static void printenv()
{
char **envp;
for (envp = environ; envp && *envp; envp++)
printf("%s\n", *envp);
}
int main(argc, argv)
int argc;
char **argv;
{
char *cp;
int changed = 0;
if (argc < 2) {
printf("usage: %s name[=value]...\n", argv[0]);
return (1);
}
while (--argc && *++argv) {
if (argv[0][0] == '-') { /* unsetenv() test */
unsetenv(argv[0] + 1);
changed = 1;
} else if (strchr(argv[0], '=') == 0) { /* getenv() test */
cp = getenv(argv[0]);
printf("%s: %s\n", argv[0], cp ? cp : "not found");
} else { /* putenv() test */
if (putenv(argv[0])) {
perror("putenv");
return (1);
}
changed = 1;
}
}
if (changed)
printenv();
return (0);
}
#endif /* TEST */
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