20.3 Interpreting Commands from a File

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For all practical purposes, any interpreter is pretty useless if it only works interactively. I have added a `source' built-in command to `sic_builtin.c' which takes lines of input from a file and evaluates them using `sic_repl.c' in much the same way as lines typed at the prompt are evaluated otherwise . Here is the built-in handler:

 
 /* List of built in functions. */ #define builtin_functions               \         BUILTIN(exit,           0, 1)   \         BUILTIN(load,           1, 1)   \         BUILTIN(source,         1, -1)  \         BUILTIN(unload,         1, -1) BUILTIN_DECLARATION (source) {   int status = SIC_OKAY;   int i;   for (i = 1; status == SIC_OKAY && argv[i]; ++i)     status = source (sic, argv[i]);   return status; } 

And the source function from `sic_repl.c' :

 
 int source (Sic *sic, const char *path) {   FILE *stream;   int result = SIC_OKAY;   int save_interactive = is_interactive;   SIC_ASSERT (sic && path);      is_interactive = 0;   if ((stream = fopen (path, "rt")) == NULL)     {       sic_result_clear (sic);       sic_result_append (sic, "cannot source \"", path, "\": ",                          strerror (errno), NULL);       result = SIC_ERROR;     }   else     result =  evalstream (sic, stream);   is_interactive = save_interactive;   return result; } 

The reason for separating the source function in this way, is that it makes it easy for the startup sequence in main to evaluate a startup file. In traditional Unix fashion, the startup file is named `.sicrc' , and is evaluated if it is present in the user 's home directory:

 
 static int evalsicrc (Sic *sic) {   int result = SIC_OKAY;   char *home = getenv ("HOME");   char *sicrcpath, *separator = "";   int len;   if (!home)     home = "";   len = strlen (home);   if (len && home[len -1] != '/')     separator = "/";   len += strlen (separator) + strlen (SICRCFILE) + 1;   sicrcpath = XMALLOC (char, len);   sprintf (sicrcpath, "%s%s%s", home, separator, SICRCFILE);   if (access (sicrcpath, R_OK) == 0)     result = source (sic, sicrcpath);   return result; } 

This document was generated by Gary V. Vaughan on May, 24 2001 using texi2html


GNU Autoconf, Automake and Libtool
GNU Autoconf, Automake, and Libtool
ISBN: 1578701902
EAN: 2147483647
Year: 2002
Pages: 290

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