Syntax error near unexpected token '('

问题:

As a beginner, I am trying to write a simple c program to learn and execute the "write" function.

I am trying to execute a simple c program simple_write.c

#include <unistd.h>
#include <stdlib.h>
int main()
{
    if ((write(1, “Here is some data\n”, 18)) != 18)
         write(2, “A write error has occurred on file descriptor 1\n”,46);
    exit(0);
}

I also execute chmod +x simple_write.c

But when i execute ./simple_write.c, it gives me syntax error near unexpected token '('

Couldn't figure out why this happens ??

P.S: The expected output is:-

$ ./simple_write
Here is some data
$

回答1:

You did

$ chmod +x simple_write.c
$ ./simple_write.c

when you should have done

$ cc simple_write.c -o simple_write
$ chmod +x simple_write                 # On second thought, you probably don’t need this.
$ ./simple_write

In words: compile the program to create an executable simple_write (without .c) file, and then run that.  What you did was attempt to execute your C source code file as a shell script.

Notes:

• The simple_write file will be a binary file.  Do not look at it with tools meant for text files (e.g., cat, less, or text editors such as gedit).

• cc is the historical name for the C compiler.  If you get cc: not found (or something equivalent), try the command again with gcc (GNU C compiler).  If that doesn’t work,

  • If you’re on a shared system (e.g., school or library), ask a system administrator how to compile a C program.
  • If you’re on your personal computer (i.e., you’re the administrator), you will need to install the compiler yourself (or get a friend to do it).  There’s lots of guidance written about this; just search for it.

• When you get to writing more complicated programs, you are going to want to use

  make simple_write
  

  which has the advantages of

  • being able to orchestrate a multi-step build, which is typical for complex programs, and
  • it knows the standard ways of compiling programs on that system (for example, it will probably “know” whether to use cc or gcc).

  And, in fact, you should be able to use the above command now.  This may (or may not) simplify your life.

---

P.S. Now that this question is on Stack Overflow, I’m allowed to talk about the programming aspect of it.  It looks to me like it should compile, but

• The first write line has more parentheses than it needs.

  if (write(1, "Here is some data\n", 18) != 18)
  

  should work.

• In the second write line, I count the string as being 48 characters long, not 46.

• By the way, do you know how to make the first write fail, so the second one will execute?  Try

  ./simple_write >&-

回答2:

You cannot execute C source code in Linux (or other systems) directly.

C is a language that requires compilation to binary format.

You need to install C compiler (the actual procedure differs depending on your system), compile your program and only then you can execute it.

Currently it was interpreted by shell. The first two lines starting with # were ignored as comments. The third line caused a syntax error.

回答3:

Ok,

I got what i was doing wrong.

These are the steps that I took to get my problem corrected:-

1. $ gedit simple_write.c

2. Write the code into this file and save it (with .c extension).

3. $ make simple_write

4. $ ./simple_write

And I got the desired output.

Thanks!!