fileio/copy.c

This is fileio/copy.c (Listing 4-1, page 71), an example from the book, The Linux Programming Interface.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

This page shows the "distribution" or "book" version of the file (why are there two versions?), or the differences between the two versions. You can switch between the views using the tabs below.

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

  Cover of The Linux Programming Interface
+/* copy.c
+
+   Copy the file named argv[1] to a new file named in argv[2].
+*/
 #include <sys/stat.h>
 #include <fcntl.h>
 #include "tlpi_hdr.h"
 
 #ifndef BUF_SIZE        /* Allow "cc -D" to override definition */
 #define BUF_SIZE 1024
 #endif
 
 int
 main(int argc, char *argv[])
 {
     int inputFd, outputFd, openFlags;
     mode_t filePerms;
     ssize_t numRead;
     char buf[BUF_SIZE];
 
     if (argc != 3 || strcmp(argv[1], "--help") == 0)
         usageErr("%s old-file new-file\n", argv[0]);
 
     /* Open input and output files */
 
     inputFd = open(argv[1], O_RDONLY);
     if (inputFd == -1)
         errExit("opening file %s", argv[1]);
 
     openFlags = O_CREAT | O_WRONLY | O_TRUNC;
     filePerms = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP |
                 S_IROTH | S_IWOTH;      /* rw-rw-rw- */
     outputFd = open(argv[2], openFlags, filePerms);
     if (outputFd == -1)
         errExit("opening file %s", argv[2]);
 
     /* Transfer data until we encounter end of input or an error */
 
     while ((numRead = read(inputFd, buf, BUF_SIZE)) > 0)
         if (write(outputFd, buf, numRead) != numRead)
             fatal("write() returned error or partial write occurred");
     if (numRead == -1)
         errExit("read");
 
     if (close(inputFd) == -1)
         errExit("close input");
     if (close(outputFd) == -1)
         errExit("close output");
 
     exit(EXIT_SUCCESS);
 }

Note that, in most cases, the programs rendered in these web pages are not free standing: you'll typically also need a few other source files (mostly in the lib/ subdirectory) as well. Generally, it's easier to just download the entire source tarball and build the programs with make(1). By hovering your mouse over the various hyperlinked include files and function calls above, you can see which other source files this file depends on.

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