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Full Discussion: touch
Top Forums Shell Programming and Scripting touch Post 302133529 by Perderabo on Thursday 23rd of August 2007 07:42:41 PM
Old 08-23-2007
The touch command is built upon the utime()/utimes() system calls. So look up those system calls for your OS to see why they might fail. My copy of AIX 5.3 docs says:
Code:
EPERM
The Times parameter is not null and the calling process neither owns the file nor has root user authority.
EACCES
The Times parameter is null, effective user ID is neither the owner of the file nor has root authority, or write access is denied.
EROFS
The file system that contains the file is mounted read-only.

Hmmm, I hope that is an error in documentation or at least the docs are unclear. It is supposed to be like this...

The effective uid must own the file and have write permission to the file or the effective uid must be root. If the Times parameter is null, we are just seeing if we could change the times if we wanted to... but we will not actually change anything if we have permission. If it fails, you get EPERM or EACCES depending on whether or not you were trying to change anything.

But if you are not root, you must own the file. This is required by Posix.
 

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UTIMES(2)						      BSD System Calls Manual							 UTIMES(2)

NAME
futimes, utimes -- set file access and modification times LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/time.h> int futimes(int fildes, const struct timeval times[2]); int utimes(const char *path, const struct timeval times[2]); DESCRIPTION
The access and modification times of the file named by path or referenced by fildes are changed as specified by the argument times. If times is NULL, the access and modification times are set to the current time. The caller must be the owner of the file, have permission to write the file, or be the super-user. If times is non-NULL, it is assumed to point to an array of two timeval structures. The access time is set to the value of the first ele- ment, and the modification time is set to the value of the second element. The caller must be the owner of the file or be the super-user. In either case, the inode-change-time of the file is set to the current time. RETURN VALUES
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error. ERRORS
The utimes() system call will fail if: [EACCES] Search permission is denied for a component of the path prefix; or the times argument is NULL and the effective user ID of the process does not match the owner of the file, and is not the super-user, and write access is denied. [EFAULT] path or times points outside the process's allocated address space. [EIO] An I/O error occurs while reading or writing the affected inode. [ELOOP] Too many symbolic links are encountered in translating the pathname. This is taken to be indicative of a looping symbolic link. [ENAMETOOLONG] A component of a pathname exceeds NAME_MAX characters, or an entire path name exceeded PATH_MAX characters. [ENOENT] The named file does not exist. [ENOTDIR] A component of the path prefix is not a directory. [EPERM] The times argument is not NULL and the calling process's effective user ID does not match the owner of the file and is not the super-user. [EROFS] The file system containing the file is mounted read-only. The futimes() system call will fail if: [EBADF] fildes does not refer to a valid descriptor. All of the functions will fail if: [EACCES] The times argument is NULL and the effective user ID of the process does not match the owner of the file, and is not the super-user, and write access is denied. [EFAULT] times points outside the process's allocated address space. [EIO] An I/O error occurred while reading or writing the affected inode. [EPERM] The times argument is not NULL and the calling process's effective user ID does not match the owner of the file and is not the super-user. [EROFS] The file system containing the file is mounted read-only. SEE ALSO
stat(2), utime(3) HISTORY
The utimes() function call appeared in 4.2BSD. The futimes() function call first appeared in FreeBSD 3.0. BSD
June 4, 1993 BSD
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