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/* * shvar.c * * Implementation of non-destructively reading/writing files containing * only shell variable declarations and full-line comments. * * Includes explicit inheritance mechanism intended for use with * Red Hat Linux ifcfg-* files. There is no protection against * inheritance loops; they will generally cause stack overflows. * Furthermore, they are only intended for one level of inheritance; * the value setting algorithm assumes this. * * Copyright 1999,2000 Red Hat, Inc. * * This is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * */ #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <unistd.h> #include "shvar.h" /* Open the file <name>, returning a shvarFile on success and NULL on failure. Add a wrinkle to let the caller specify whether or not to create the file (actually, return a structure anyway) if it doesn't exist. */ static shvarFile * svOpenFile(const char *name, gboolean create) { shvarFile *s = NULL; int closefd = 0; s = g_malloc0(sizeof(shvarFile)); s->fd = open(name, O_RDWR); /* NOT O_CREAT */ if (s->fd == -1) { /* try read-only */ s->fd = open(name, O_RDONLY); /* NOT O_CREAT */ if (s->fd != -1) closefd = 1; } s->fileName = g_strdup(name); if (s->fd != -1) { struct stat buf; char *p, *q; if (fstat(s->fd, &buf) < 0) goto bail; s->arena = g_malloc0(buf.st_size + 1); if (read(s->fd, s->arena, buf.st_size) < 0) goto bail; /* we'd use g_strsplit() here, but we want a list, not an array */ for(p = s->arena; (q = strchr(p, '\n')) != NULL; p = q + 1) { s->lineList = g_list_append(s->lineList, g_strndup(p, q - p)); } /* closefd is set if we opened the file read-only, so go ahead and close it, because we can't write to it anyway */ if (closefd) { close(s->fd); s->fd = -1; } return s; } if (create) { return s; } bail: if (s->fd != -1) close(s->fd); if (s->arena) g_free (s->arena); if (s->fileName) g_free (s->fileName); g_free (s); return NULL; } /* Open the file <name>, return shvarFile on success, NULL on failure */ shvarFile * svNewFile(const char *name) { return svOpenFile(name, FALSE); } /* Create a new file structure, returning actual data if the file exists, * and a suitable starting point if it doesn't. */ shvarFile * svCreateFile(const char *name) { return svOpenFile(name, TRUE); } /* remove escaped characters in place */ static void unescape(char *s) { int len, i; len = strlen(s); if ((s[0] == '"' || s[0] == '\'') && s[0] == s[len-1]) { i = len - 2; memmove(s, s+1, i); s[i+1] = '\0'; len = i; } for (i = 0; i < len; i++) { if (s[i] == '\\') { memmove(s+i, s+i+1, len-(i+1)); len--; } s[len] = '\0'; } } /* create a new string with all necessary characters escaped. * caller must free returned string */ static const char escapees[] = "\"'\\$~`"; /* must be escaped */ static const char spaces[] = " \t|&;()<>"; /* only require "" */ static char * escape(const char *s) { char *new; int i, j, mangle = 0, space = 0; int newlen, slen; static int esclen, splen; if (!esclen) esclen = strlen(escapees); if (!splen) splen = strlen(spaces); slen = strlen(s); for (i = 0; i < slen; i++) { if (strchr(escapees, s[i])) mangle++; if (strchr(spaces, s[i])) space++; } if (!mangle && !space) return strdup(s); newlen = slen + mangle + 3; /* 3 is extra ""\0 */ new = g_malloc0(newlen); if (!new) return NULL; j = 0; new[j++] = '"'; for (i = 0; i < slen; i++) { if (strchr(escapees, s[i])) { new[j++] = '\\'; } new[j++] = s[i]; } new[j++] = '"'; g_assert(j == slen + mangle + 2); /* j is the index of the '\0' */ return new; } /* Get the value associated with the key, and leave the current pointer * pointing at the line containing the value. The char* returned MUST * be freed by the caller. */ char * svGetValue(shvarFile *s, const char *key) { char *value = NULL; char *line; char *keyString; int len; g_assert(s); g_assert(key); keyString = g_malloc0(strlen(key) + 2); strcpy(keyString, key); keyString[strlen(key)] = '='; len = strlen(keyString); for (s->current = s->lineList; s->current; s->current = s->current->next) { line = s->current->data; if (!strncmp(keyString, line, len)) { value = g_strdup(line + len); unescape(value); break; } } g_free(keyString); if (value) { if (value[0]) { return value; } else { g_free(value); return NULL; } } if (s->parent) value = svGetValue(s->parent, key); return value; } /* return 1 if <key> resolves to any truth value (e.g. "yes", "y", "true") * return 0 if <key> resolves to any non-truth value (e.g. "no", "n", "false") * return <default> otherwise */ int svTrueValue(shvarFile *s, const char *key, int def) { char *tmp; int returnValue = def; tmp = svGetValue(s, key); if (!tmp) return returnValue; if ( (!strcasecmp("yes", tmp)) || (!strcasecmp("true", tmp)) || (!strcasecmp("t", tmp)) || (!strcasecmp("y", tmp)) ) returnValue = 1; else if ( (!strcasecmp("no", tmp)) || (!strcasecmp("false", tmp)) || (!strcasecmp("f", tmp)) || (!strcasecmp("n", tmp)) ) returnValue = 0; g_free (tmp); return returnValue; } /* Set the variable <key> equal to the value <value>. * If <key> does not exist, and the <current> pointer is set, append * the key=value pair after that line. Otherwise, prepend the pair * to the top of the file. Here's the algorithm, as the C code * seems to be rather dense: * * if (value == NULL), then: * if val2 (parent): change line to key= or append line key= * if val1 (this) : delete line * else noop * else use this table: * val2 * NULL value other * v NULL append line noop append line * a * l value noop noop noop * 1 * other change line delete line change line * * No changes are ever made to the parent config file, only to the * specific file passed on the command line. * */ void svSetValue(shvarFile *s, const char *key, const char *value) { char *newval = NULL, *val1 = NULL, *val2 = NULL; char *keyValue; g_assert(s); g_assert(key); /* value may be NULL */ if (value) newval = escape(value); keyValue = g_strdup_printf("%s=%s", key, newval ? newval : ""); val1 = svGetValue(s, key); if (val1 && newval && !strcmp(val1, newval)) goto bail; if (s->parent) val2 = svGetValue(s->parent, key); if (!newval || !newval[0]) { /* delete value somehow */ if (val2) { /* change/append line to get key= */ if (s->current) s->current->data = keyValue; else s->lineList = g_list_append(s->lineList, keyValue); s->freeList = g_list_append(s->freeList, keyValue); s->modified = 1; } else if (val1) { /* delete line */ s->lineList = g_list_remove_link(s->lineList, s->current); g_list_free_1(s->current); s->modified = 1; goto bail; /* do not need keyValue */ } goto end; } if (!val1) { if (val2 && !strcmp(val2, newval)) goto end; /* append line */ s->lineList = g_list_append(s->lineList, keyValue); s->freeList = g_list_append(s->freeList, keyValue); s->modified = 1; goto end; } /* deal with a whole line of noops */ if (val1 && !strcmp(val1, newval)) goto end; /* At this point, val1 && val1 != value */ if (val2 && !strcmp(val2, newval)) { /* delete line */ s->lineList = g_list_remove_link(s->lineList, s->current); g_list_free_1(s->current); s->modified = 1; goto bail; /* do not need keyValue */ } else { /* change line */ if (s->current) s->current->data = keyValue; else s->lineList = g_list_append(s->lineList, keyValue); s->freeList = g_list_append(s->freeList, keyValue); s->modified = 1; } end: if (newval) free(newval); if (val1) free(val1); if (val2) free(val2); return; bail: if (keyValue) free (keyValue); goto end; } /* Write the current contents iff modified. Returns -1 on error * and 0 on success. Do not write if no values have been modified. * The mode argument is only used if creating the file, not if * re-writing an existing file, and is passed unchanged to the * open() syscall. */ int svWriteFile(shvarFile *s, int mode) { FILE *f; int tmpfd; if (s->modified) { if (s->fd == -1) s->fd = open(s->fileName, O_WRONLY|O_CREAT, mode); if (s->fd == -1) return -1; if (ftruncate(s->fd, 0) < 0) return -1; tmpfd = dup(s->fd); f = fdopen(tmpfd, "w"); fseek(f, 0, SEEK_SET);


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