diff options
Diffstat (limited to 'environ.c')
| -rw-r--r-- | environ.c | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/environ.c b/environ.c new file mode 100644 index 0000000..e7f846d --- /dev/null +++ b/environ.c @@ -0,0 +1,224 @@ +/* + * 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 */ |