cross platform Ch Shell Programming

Keyboard shortcuts in Ch shell

 C:/> cd c:/do[TAB]
 Documents/ Documents and Settings/
 C:/> cd c:/Documents\ [TAB]
 C:/> cd "c:/Documents and Settings"/

Ch Extensions to C for Shell Programming and Scripting

• Ch can be used in either command shell or program mode interpretively.
  Ch language environment can be used as a command shell. In command shell, history substitution, event designator, quick substitution, command substitution, aliases, and file or directory name completion using a tab key are available in Ch. An example of Ch shell in action is given as follows:

  > hello.c
   Hello, world!
   (execute the famous hello.c program without compilation)
  > int i, *p;
  > p = &i; 
  > *p = 90;
  > printf("i = %d\n", i);
   i = 90
  >if (i == 90) printf("good\n"); else printf("bad\n");
   good
  > int **p2
  > p2 = &p
  > printf("**p2 = %d\n", **p2)
   **p2 = 90
  > ls *> junkfile
   (all file names go to junkfile)
  > i**p
   8100
  > array int a[2][3]
  > a = (array int [2][3])5
  > a
   5 5 5 
   5 5 5
  > 2*transpose(a)
   10 10 
   10 10 
   10 10 
  > which ls
   ls is aliased to ls -F // if ls is an alias set in ~/[_]chrc
  >
  > int i;
  > for (i=0; i<6;i++) printf("%d\n",i); 0 1 2 3 4 5>
  

• A quick calculator
  

   #return to get the calculation result from ch shell
  > 5*9-4+334-(5*9)*2
   285
  >
  

• POSIX
  Ch supports POSIX for across platform directory and file processing. Sample code can be found here.

• String data type
  C is a small language; it has no string data type. Pointers to char are handled as strings in C. Ch provides an alternative string data type for pointers. It eliminates potential bugs before they happen. The string data type can also be used with existing C functions and C data type of 'pointers to char'. For shell programming, a string data type is added to C in Ch. It is seamlessly merged with pointer to char. All functions defined in the standard C library header string.h are valid for both pointers to char and strings. String is a first-class object in Ch. For example, the following code fragment

   string_t s, a[3];
   s = "great string"
   s = stradd("greater ", s)
   strcpy(a[0], s);
   printf("a[0] = %s\n", a[0]);
  

  will display greater great string.

• Foreach-loop is added for shell iteration.
  The code below will create three directories dir1, dir2 and dir3 in the current directory.

   string_t token, str="dir1 dir2 dir3";
   foreach(token; str) {
   mkdir $token;
   }
  

• Here document and Verbatim output. The Here document and verbatim output features can be achieved using the code block feature of function fprintf. The Ch function sendApplet() below generates a C program. void sendApplet(char *x, char *y, char *expr) { fprintf(stdout, "#include<stdio.h>\n"); fprintf(stdout, "int main() {\n"); fprintf(stdout, " double x = %s;\n", x); fprintf(stdout, " double y = %s;\n", y); fprintf(stdout, " printf(\"x = %%f, \", x);\n"); fprintf(stdout, " printf(\"y = %%f \\n\", y);\n"); fprintf(stdout, " printf(\"%s = %%f\\n\", %s);\n", expr, expr); fprintf(stdout, "}\n"); } The above function sendApplet() can be rewritten in Ch as follows. If you want to redirect to a file instead of 'stdout', you can simple open a file and replace 'stdout' below with your file handler. void sendApplet(char *x, char *y, char *expr) { fprintf stdout << ENDFILE #include<stdio.h> int main() { double x = $x; double y = $y; printf("x = %f", x); printf("y = %f\n", y); printf("$expr = %f\n", $expr); } ENDFILE }

• The controlling variable of the switch and case statement can be a string in addition to integral type. #!/bin/ch char *ch="SoftIntegration Ch"; float version=2; string_t hostname=`hostname`; switch (hostname) { case "mymachine": printf("Hello world\n"); break; case "testmachine": fprintf stdout << ENDPRINT Welcome to use $ch version $version SoftIntegration, Inc. ENDPRINT echo Ch is cool! I can now use a C program to backup files dump 0ubdsf 80 50000 50000 /dev/nrst0 /dev/sd0a break; default: break; }

  If you want to prevent the variable or expression substitution for '$', you can precede the '$' with '\'. '$' is passed unchanged if followed by a blank, tab, or end-of-line.
  

• Variable substitution and command substitution with combination of shell commands and C code
  Shell commands such as sed, awk, wc, grep, etc. can be combined with C code to run in Ch with variable substitution and command substitution. Executable programs can also be used directly in a Ch script. Below is an example: #!/bin/ch string_t result1; char result2[50]; grep "test" myfile.txt; if ( _status == 0 ) { printf(" 'test' is found in myfile.txt\n"); } else { printf("Cannot find 'test' in myfile.txt\n"); } result1=`wc -l /etc/passwd`; echo $result1; strcpy(result2, `wc -l /etc/passwd`); printf("%s\n", result2); The output for result1 and result2 are the same in the above program.

• Safe Ch is designed for the growing need of internet computing.
  In addition to restrictions imposed by conventional restricted shell, many other features are disabled in safe Ch for across-network internet computing. A system administrator may grant limited access to users using safe Ch.

• System variables _argc and _argv for command line argument interface.
  System variables _argc and _argv are equivalent to arguments argc and argv in startup C function

   int main(int argc, char *argv[]);
  

  Assume program cpfile.ch contains the following statements.

   #!/bin/ch
   cp /dir/source/$(_argv[1]) /dir/dest/
  

  Program cpfile.ch can be used to copy any file located at directory /dir/source to directory /dir/dest. For example, the following commands

  > cpfile file1
  > cpfile file2
  

  will copy files file1 and file2 from directory /dir/source to directory /dir/dest.

• FAQ
  • How to define a C/Ch/C++ function from Ch shell command prompt?
  • How to load a C/Ch/C++ script program and call its functions from Ch shell command prompt interactively?
  • How to call one user-defined function or multiple user-defined functions from Ch?
  • How to unload defined functions and variables from ch shell or programs?

Ch shell runs slightly different in Windows and Unix.

• command substitution
  In windows ch shell, the following command substitution is supported.

  > `date`
  > char *a=`date`; 
  > echo $a
   Wed Nov 26 21:12:23 Pacific Standard Time 2011
  

  However, Ch shell in Windows doesn't support the following command substituion.

  > echo `date`
  

  In Unix Ch shell, they are all supported.

• background process
  In windows, Ch shell supports background process ( & ) for win32 GUI applications, not the unix utilities. For example: "ls & " doens't work. however, "notepad &" works fine. In Unix, there is no such a problem in Ch shell.

• stdout and stderr redirect
  

  > ch -r command>filename  (in both Windows and Unix) 
  > command>filename 2>&1  (in Unix) 
  > command 1>filename 2>&1  (in Windows)
  

• path
  In Unix, ch shell works the same as bash or csh. The working directory in Ch shell in windows differs from cygwin and msdos shell.
  Ch shell cygwin or unix shell in windows MSDOS shell

  working directory c:/Users/username /c/Users/username c:\Users\username

• Example 1
  The following Ch shell script can be used to backup file systems.

   #include<stdio.h>
   int main () {
   printf("Hello, world!\n");
   echo Ch is cool! I can now use a C program to backup files
   dump 0ubdsf 80 50000 50000 /dev/nrst0 /dev/sd0a
   }
  

• Example 2 with Read eval print loop (REPL) features.
  

  double x;
  x = 2.5;
  x = streval("2*x")
  printf("x = %.2lf\n", x);
  

  ---

  The output is 5.00.

• Example 3
  The example below will print out all sub-directories and files in the current directory, as well as the full command path for command gzip.

  
   #!/bin/ch
   #include <stdio.h>
   char *s;
   int i=0;
   foreach (s;`ls`) {
   i++;
   echo $s;
   }
   printf("the total number of directory and files are %d\n",i);
   s =`which gzip`;
   echo $s;
  
  

• Example 4
  Below is another sample shell script.

   #!/bin/ch
   int main() {
   char *s = "pointer to char";
   int i; 
   float f, *p;
   f = 6; 
   p= &f;
   printf("s = %s\n", s);
   printf("*p = %f\n", f);
   /* output from the following statement is "6 6 pointer to char o" */
   echo $f $(*p) $s $(*(s+1));
   pwd
   ls> junk
   }
  

• Example 5
  The following shell commands in Bourne Shell sh #!/bin/sh command argument << EOF input from the console command line abcd EOF can be handled in Ch as follows: #!/bin/ch #include <stdio.h> FILE *fp; string_t command_args="input from the console command line\nabcd"; fp = popen("command", "w"); fwrite(command_args, strlen(command_args), sizeof(char), fp); pclose(fp);
• Example 6
  List all commands available anywhere in your path in Unix. #!/bin/ch #include <unistd.h> string_t dir, file; /* define string type */ foreach (dir; `echo $PATH &#124; tr ":" " "`) { foreach (file; `ls $dir`) { if (access (dir/file, X_OK) ==0 ) { echo $dir/$file; } } }
• Example 7
  Find and compile all .c files into .o in the current directory when the .o is old or absent. #!/bin/ch #include <sys/stat.h> struct stat cstat, ostat; string_t c, o; foreach (c; `find . -name "*.c"`) { o=`echo $c &#124; sed 's/.c$/.o/'`; stat(o, &ostat); stat(c, &cstat); if (ostat.st_mtime> cstat.st_mtime) { echo "compiling $c to $o"; gcc -c -o "$o" "$c"; } }
• Example 8
  Uses awk in Ch shell. cat file_name &#124; awk "{print \1ドル}" awk "{print \1ドル}" < file_name