# /etc/hosts
# IPaddress(IPv4)  FQDN(Fully Qualified Domain Name)  ALIAS

127.0.0.1      localhost.localdomain  localhost
192.168.0.1    gateway.localdomain      gateway
	192.168.0.2    hoge.localdomain       # comment

100.100.0.     badip.localdomain

IP='127.0.0.1' FQDN='localhost.localdomain' ALIAS='localhost'
IP='192.168.0.1' FQDN='gateway.localdomain' ALIAS='gateway'
IP='192.168.0.2' FQDN='hoge.localdomain'
IP='100.100.0.' FQDN='badip.localdomain'

#include <stdio.h>
#include <string.h>
#include <ctype.h>

static void analyze_etchosts_noregex(void)
{
  char buf[BUFSIZ];
  char tokens[3][BUFSIZ];
  char *p;
  int  n;
  
  while( fgets(buf,sizeof(buf),stdin) != (char*)NULL ) {
    /* reset tokens buffer */
    *tokens[0] = *tokens[1] = *tokens[2] = (char)NULL;

    /* eliminate comment and newline*/;
    if( (p=strchr( buf,(int)'#'))  != NULL ) *p = (char)NULL;
    if( (p=strchr( buf,(int)'\n')) != NULL ) *p = (char)NULL;

    /* search IP address */
    p = buf;
    n = 0;
    for(;;) {
      while( !(isgraph((int)*p)!=0 || *p==(char)NULL) ) p++;
      if( *p != (char)NULL ) {
	char *t;
	t = tokens[n];
	/* copying to tokens buffer */
	while( !(isgraph((int)*p)==0||*p==(char)NULL) ) *t++ = *p++;
	*t = (char)NULL;
	n++;
	if( n==3 ) break;
      } else break;
    }

    if( strlen(tokens[0])>0 && strlen(tokens[1])>0 ) { 
      printf("IP='%s' FQDN='%s'",tokens[0],tokens[1]);
      if( strlen(tokens[2])>0 ) {
	printf(" ALIAS='%s'",tokens[2]);
      }
      puts("");
    }
  }
}

int main(int argc, char *argv[])
{
  analyze_etchosts_noregex();
  return 0;
}

$ cc -Wall -o parse_hosts parse_hosts.c
$ ./parse_hosts < hosts.example

#include <stdio.h>
#include <string.h>
#include <regex.h>

static void analyze_etchosts_regex(void)
{
  regex_t preg;
  char buf[BUFSIZ];
  char *regex = "([.0-9]+)[ \t]+([^ \t#]+)([ \t]+([^ \t#]+)) ";
  regmatch_t   pmatch[5];

  regcomp(&preg,regex,REG_EXTENDED|REG_NEWLINE);

  while( fgets(buf,sizeof(buf),stdin) != (char*)NULL ) {
    if( regexec(&preg,buf,5,pmatch,0) != REG_NOMATCH ) {
      printf("IP='%.*s' FQDN='%.*s'",
	     pmatch[1].rm_eo-pmatch[1].rm_so,&buf[pmatch[1].rm_so],
	     pmatch[2].rm_eo-pmatch[2].rm_so,&buf[pmatch[2].rm_so]);
      if( pmatch[3].rm_eo!=-1 ) {
	printf(" ALIAS='%.*s'",
	       pmatch[4].rm_eo-pmatch[4].rm_so,&buf[pmatch[4].rm_so]);
      }
      puts("");
    }
  }  
  regfree(&preg);
}

int main(int argc, char *argv[])
{
  analyze_etchosts_regex();
  return 0;
}

$ cc -Wall -o parse_hosts_regex parse_hosts_regex.c
$ ./parse_hosts_regex < hosts.example

全てのサービスのリストを表示する。
$ ./chkinetcfg list
on  : echo       stream     tcp  
on  : echo       dgram      udp 
        ...
off : telnet     stream     tcp       # コメント化されている
        ...

特定のサービスのリストを表示する。
$ ./chkinetcfg list  telnet
off : telnet     stream     tcp 

telnetのコメントを外した設定ファイルを標準出力に出す
$ ./chkinetcfg on telnet > inetd.conf.telnet-on

echoを無効にするためにコメント化する。その設定ファイルを標準出力に出す
$ ./chkinetcfg off echo > inetd.conf.echo-off
				

$ ./chkinetcfg list echo/tcp
on  : echo       stream     tcp  

/* ------------------------------------------------------------
   This program is one of examples of grep implementation with 
   the regex() function in the GNU C library.

   written by Kazutomo Yoshii  

   This program is free software; you can redistribute it and/or modify
   it under ther terms of GNU General Public License, version 2.  See
   COPYING for more detail.
   ------------------------------------------------------------ */
#include <stdio.h>
#include <string.h>
#include <regex.h>

#define SG_COUNTNOMATCHES    (1<<0)
#define SG_IGNORECASE        (1<<1)
#define SG_MATCHEDFILENAME   (1<<2)
#define SG_LINENO            (1<<3)
#define SG_TWOORMOREFILES    (1<<4)

static int simple_grep(char *regex,char *filename,int options )
{
  FILE    *fp;
  regex_t preg;
  int     rc;
  char    buf[BUFSIZ];
  char    errbuf[BUFSIZ];
  int     lineno=1;
  int     n_matches=0;

  if(filename) {
    fp = fopen( filename,"r");
    if( !fp ) {
      perror("fopen");
      return 1;
    }
  } else {
    fp = stdin;
  }

  if( options&SG_IGNORECASE ) {
    rc = regcomp(&preg,regex,REG_EXTENDED|REG_NEWLINE|REG_ICASE);
  } else {
    rc = regcomp(&preg,regex,REG_EXTENDED|REG_NEWLINE);
  }

  if( rc ) {
    regerror(rc, &preg, errbuf, sizeof(errbuf) );
    printf("error: %s\n", errbuf);
    return 1;
  }

  while( fgets(buf,sizeof(buf),fp) != (char*)NULL ) {
    if( regexec(&preg,buf,0,NULL,0) != REG_NOMATCH ) {
      n_matches++;

      if( (options&SG_COUNTNOMATCHES)==0 &&
	  (options&SG_MATCHEDFILENAME)==0 ) {
	if(options&SG_TWOORMOREFILES ) {
	  printf("%s:", filename);
	}
	if( options&SG_LINENO) {
	  printf("%d:%s", lineno, buf);
	} else {
	  printf("%s", buf);
	}
      } else if( (options&SG_MATCHEDFILENAME) ) {
	break;
      }
    }
    lineno++;
  }

  if( (options&SG_COUNTNOMATCHES) ) {
    if(options&SG_TWOORMOREFILES ) {
      printf("%s:", filename);
    }
    printf("%d\n", n_matches);
  }

  if( (options&SG_MATCHEDFILENAME) ) {
    if( fp == stdin ) {
      puts("(standard input)");
    } else {
      printf("%s\n", filename); 
    }
  }

  regfree(&preg);

  if( fp != stdin ) {
    fclose(fp);
  }

  return 0;
}

static void print_usage(void)
{
  puts("Usage: simple-grep [OPTIONS] PATTERN [FILE...]");
  puts("");
  puts("[OPTIONS]");
  puts("");
  puts("-c : Suppress  normal  output;  instead print a count of");
  puts("     matching lines for each input file.");
  puts("");
  puts("-i : Ignore  case  distinctions  in the PATTERN");
  puts("");
  puts("-l : Suppress  normal  output; instead print the name of");
  puts("     each input file from which  output  would  normally");
  puts("     have  been  printed.  The scanning will stop on the");
  puts("     first match.");
  puts("");
  puts("-n : Prefix each line of output  with  the  line  number");
  puts("     within its input file.");
  puts("");
}

int main(int argc, char *argv[] )
{
  char *regex;
  int  options = 0;
  int  i,rc;

  if( argc < 2 ) {
    print_usage();
    return 1;
  }

  for(i=1; i  

/* ------------------------------------------------------------
   chkinetcfg is free software; you can redistribute it and/or modify
   it under ther terms of GNU General Public License, version 2.  See
   COPYING for more detail.

   Written by Kazutomo Yoshii  
   ------------------------------------------------------------ */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <regex.h>

#define INETDCONF   ("/etc/inetd.conf")

#define INETDENT_REGEX_STR    ("([[:punct:]]) [[:blank:]]*"\
      "([[:graph:]]+)[[:blank:]]+"\
      "(stream|dgram|rdm|seqpacket|raw)[[:blank:]]+"\
      "([[:alnum:]]+)[[:blank:]]+"\
      "(wait|nowait)([.0-9]+) [[:blank:]]+" \
      "([[:alnum:]]+)([.[:alnum:]]+) [[:blank:]]+"\
      "([/[:alnum:]]+)[[:blank:]]*"\
      "(.*)")

typedef struct _inetd_conf {
  struct _inetd_conf *next;
  char *line;     /* buffer for each line */
  char *name;     /* if name is NULL, means line doesn't contain service */
  char *socktype;
  char *proto;
  int  iscomment; /* val=1 means that service is commneted */
} InetdConf;

static void removeInetdConfList(InetdConf *ptr)
{
  while(ptr) {
    InetdConf *next;

    if( ptr->line ) free(ptr->line);
    if( ptr->name ) free(ptr->name);
    if( ptr->socktype ) free(ptr->socktype);
    if( ptr->proto ) free(ptr->proto);
    next = ptr->next;
    free(ptr);
    ptr = next;
  }
}

static InetdConf *newInetdConf(char *line,regmatch_t *pmatch)
{
  InetdConf *elem;

  elem = (InetdConf*)malloc(sizeof(InetdConf));
  if( !elem ) {
    perror("malloc");
    exit(1);
  }
  memset( elem,0,sizeof(InetdConf) ); 

  elem->line = strdup(line);
  if( pmatch ) {
    char tmp[BUFSIZ];

    sprintf(tmp,"%.*s", 
	    pmatch[2].rm_eo-pmatch[2].rm_so,&line[pmatch[2].rm_so]);
    elem->name = strdup(tmp);
    sprintf(tmp,"%.*s", 
	    pmatch[3].rm_eo-pmatch[3].rm_so,&line[pmatch[3].rm_so]);
    elem->socktype = strdup(tmp);
    
    sprintf(tmp,"%.*s", 
	    pmatch[4].rm_eo-pmatch[4].rm_so,&line[pmatch[4].rm_so]);
    elem->proto = strdup(tmp);
      
    if( line[pmatch[1].rm_so] == '#' ) {
      elem->iscomment = 1;
    }
  }

  return elem; 
}

static InetdConf *readInetdConfList(void)
{
  FILE *fp;
  char buf[BUFSIZ];
  InetdConf *conf = NULL;
  InetdConf *lastconf = NULL;
  regex_t preg;
  regmatch_t   pmatch[11];
  int     rc;
  char    errbuf[BUFSIZ];

  rc = regcomp(&preg,INETDENT_REGEX_STR,REG_EXTENDED|REG_NEWLINE);
  if( rc ) {
    regerror(rc, &preg, errbuf, sizeof(errbuf) );
    printf("error: %s\n", errbuf);
    return NULL;
  }

  fp = fopen( INETDCONF, "r" );
  if( !fp ) {
    printf("can't open %s\n", INETDCONF);
    return NULL;
  }

  while( fgets(buf, sizeof(buf),fp ) != (char*)NULL ) {
    InetdConf *newelem;
    if( regexec(&preg,buf,11,pmatch,0) != REG_NOMATCH ) {
      newelem = newInetdConf(buf,pmatch);
    } else {
      newelem = newInetdConf(buf,NULL);
    }
    if( !conf ) {
      lastconf = conf = newelem;
    } else {
      lastconf->next = newelem;
      lastconf = newelem;
    }
  }

  fclose(fp);
  regfree(&preg);

  return conf;
}

static void  switch_services(InetdConf *conf,char *on_off, char *name)
{
  int flag;
  while(conf) {
    flag = 0;
    if( conf->name ) {
      if( strcmp(conf->name, name)==0 ) {
	if( strcmp(on_off,"on")==0 && conf->iscomment==1 ) {
	  printf("%s", &(conf->line[1]));
	  flag =1; 
	} else if( strcmp(on_off,"off")==0 && conf->iscomment==0 ) {
	  printf("#%s", conf->line);
	  flag =1; 
	} 
      }
    }
    if( flag==0 ) printf("%s", conf->line);
    conf= conf->next;
  }
}

static void print_line(int iscomment,char *name,char *socktype,char *proto)
{
  printf("%s : %-10s %-10s %-10s\n",
	 (iscomment==1) "off":"on ",
	 name, socktype, proto);
}

static void  list_services(InetdConf *conf,char *name)
{
  while(conf) {
    if( conf->name ) {
      if( name ) {
	if( strcmp(conf->name, name)==0 ) {
	    print_line(conf->iscomment,conf->name,conf->socktype,conf->proto);
	}
      } else {
	print_line(conf->iscomment,conf->name,conf->socktype,conf->proto);
      }
    }
    conf= conf->next;
  }
}


static void usage(void)
{
  puts("");
  puts("Usage: chkinetcfg command [name]");
  puts("");
  puts("[command]");
  puts("\tlist : this command shows all services if service isn't specified.");
  puts("\t       if service is specified,information in only display");
  puts("\t       about name,socktype and proto.");
  puts("");
  puts("\ton   : this command turns on service which service is specified");
  puts("\t       with making un-comment of the target line."); 
  puts("");
  puts("\toff  : this command turns off service which service is specified");
  puts("\t       with making comment of the target line."); 
}

int main(int argc, char *argv[]) 
{
  InetdConf *conf;
  if( argc <2 ){
    usage();
    return 1;
  }

  conf = readInetdConfList();

  if( strcmp(argv[1], "list")==0 ) {
    if( argc == 3 )  list_services(conf,argv[2]);
    else             list_services(conf,NULL);
  } else if( strcmp(argv[1], "on")==0 || 
	     strcmp(argv[1], "off")==0 ) {
    if( argc == 3 )  switch_services(conf,argv[1],argv[2]);
    else {
      printf("Please specify the service name.\n");
      usage();
      return 1;
    }
  } else {
    printf("Unknown command : '%s'\n", argv[1]);
    usage();
    return 1;
  }

  removeInetdConfList(conf);

  return 0;
}