builtins.cc

      //  $Id: builtins.cc,v 1.3 2003/04/11 03:48:16 vickery Exp $
      
      /*    Definitions of functions for jsh builtin commands.
       *
       *      $Log: builtins.cc,v $
       *      Revision 1.3  2003/04/11 03:48:16  vickery
       *      Implemented doAlias and doUnalias completely.
       *
       *      Revision 1.2  2003/04/04 23:32:28  vickery
       *      Added doChdir and doEcho builtins.
       *
       *      Revision 1.1  2003/04/04 22:37:45  vickery
       *      Initial revision
       *
       */
      
      #include "jsh.h"
      #include "alias_table.h"
      
      #include <stdio.h>
      #include <stdlib.h>
      #include <string.h>
      #include <unistd.h>
      
      //  Hack to get WIFEXITED to recognize "return JSH_ERR_RETURN"
      //  as equivalent to "exit( 1 )".
      #define JSH_ERR_RETURN  256
      
      //  doUnalias()
      //  ------------------------------------------------------------------
      /*
       *  Deletes an alias.
       */
        int
        doUnalias( const int argc, const char *argv[] )
        {
          if ( argc != 2 )
          {
            fprintf( stderr, "Usage: unalias <name>\n" );
            return JSH_ERR_RETURN;
          }
          if ( deleteAlias( argv[1] ) != 1 )
          {
            return JSH_ERR_RETURN;
          }
          return 0;
        }
      
      
      //  doAlias()
      //  ------------------------------------------------------------------
      /*
       *  Displays current aliases or defines a new one.
       *
       *    With no arguments, list all aliases.
       *    With one argument, list the named alias
       *    With two or more arguments, define a new one or replace existing
       *    one.
       */
        int
        doAlias( const int argc, const char *argv[] )
        {
          if ( 1 == argc )
          {
            listAliases();
            return 0;
          }
      
          //  Add or replace an alias
          //  --------------------------------------------------------------
          //  Create a single value from all arguments after the name
          int len = 1;
          for (int i = 2; i < argc; i++ )
          {
            len += strlen( argv[i] );
          }
          if ( 1 == len )
          {
            //  No value: list value, if there is one.
            const char *value = lookupAlias( argv[1] );
            if ( value != 0 )
            {
              printf( "alias %s = %s\n", argv[1], value );
            }
            else
            {
              printf( "alias: \"%s\" is not defined\n", argv[1] );
            }
          }
          else
          {
            char *key   = (char *) malloc( 1 + strlen( argv[1] ) );
            err_check( "malloc alias key", __FILE__, __LINE__ );
            strcpy( key, argv[1] );
            char *value = (char *) malloc( len );
            err_check( "malloc alias", __FILE__, __LINE__ );
            strcpy( value, argv[2] );
            for( int i = 3; i < argc; i++ )
            {
              strcat( value, argv[i] );
            }
            defineAlias( key, value );
          }
          return 0;
        }
          
      
      //  doChdir()
      //  ------------------------------------------------------------------
      /*
       *  Changes the shell's working directory.
       */
        int
        doChdir( const int argc, const char *argv[] )
        {
          switch ( argc )
          {
            case 1:
              {
                char *home = getenv( "HOME" );
                if ( 0 == home )
                {
                  fprintf( stderr, "Unable to determine home directory\n" );
                  return JSH_ERR_RETURN;
                }
                if ( -1 == chdir( home ) )
                {
                  perror( home );
                  return JSH_ERR_RETURN;
                }
                return 0;
                break;
              }
      
            case 2:
              if ( -1 == chdir( argv[1] ) )
              {
                perror( argv[1] );
                return JSH_ERR_RETURN;
              }
              return 0;
              break;
      
            default:
              fprintf(stderr, "Usage: cd [<directory>]\n" );
              return JSH_ERR_RETURN;
              break;
              
          }
        }
      
      //  doEcho()
      //  ------------------------------------------------------------------
      /*
       *  Echoes command line arguments.
       */
        int
        doEcho( const int argc, const char *argv[] )
        {
          for (int i = 1; i < argc; i++ )
          {
            printf( "%s ", argv[i] );
          }
          printf( "\n" );
          return 0;
        }
        
      //  doExit()
      //  ------------------------------------------------------------------
      /*
       *  Exits the shell.
       */
        int
        doExit( const int argc, const char *argv[] )
        {
          if ( argc > 2 )
          {
            fprintf( stderr, "Usage: exit <number>\n" );
            return JSH_ERR_RETURN;
          }
          if ( argc > 1 )
          {
            exit( strtol( argv[1], 0, 0 ) );
          }
          else
          {
            exit( 0 );
          }
        }