globas.h中定义  
//LoadRunner中没有直接的函数支持查找并替换字符串,因此可以封装一个lr_replace函数出来:
// ----------------------------------------------------------------------------
char *strReplace(const char *src, const char *from, const char *to)
{
  char *value;
  char *dst;
  char *match;
  int size;
  int fromlen;
  int tolen;
  size = strlen(src) + 1;
  fromlen = strlen(from);
  tolen = strlen(to);
  
  value = (char *)malloc(size);
  dst = value;
  if ( value != NULL )
  {
    for ( ;; )
    {
     
      match = (char *) strstr(src, from);
      if ( match != NULL )
      {
        size_t count = match - src;
        char *temp;
        size += tolen - fromlen;
        temp = (char *)realloc(value, size);
        if ( temp == NULL )
        {
          free(value);
          return NULL;
        }
        dst = temp + (dst - value);
        value = temp;
        memmove(dst, src, count);
        src += count;
        dst += count;
        memmove(dst, to, tolen);
        src += fromlen;
        dst += tolen;
      }
      else
      {
        strcpy(dst, src);
        break;
      }
    } 
  }
  return value;
}
// ----------------------------------------------------------------------------
// ----------------------------------------------------------------------------
int lr_replace( const char *lrparam, char *findstr, char *replacestr )
{
  int res = 0;
  char *result_str;
  char lrp[1024];
  sprintf( lrp, "{%s}", lrparam);
  result_str = strReplace( lr_eval_string(lrp), findstr, replacestr );
  if (result_str != NULL )
  {
    lr_save_string( result_str, lrparam );
    free( result_str );
    res = 1;
  }
  return res;
}
在Action中定义:
login()
{
lr_save_string("This is a string", "MyPar");
//web_convert_param( "MyPar",
//                   "SourceEncoding=PLAIN",
//                   "TargetEncoding=URL", LAST); 
lr_output_message("%s", lr_eval_string("{MyPar}"));
//lr_replace("MyPar", "+", "%20" );
//lr_output_message("%s", lr_eval_string("{MyPar}"));
lr_replace("MyPar", "ing", "旺仔" );   //将Mypar中的ing字符串用旺仔替换
lr_output_message("%s", lr_eval_string("{MyPar}"));
 
原文:http://www.cnblogs.com/qmfsun/p/4575419.html