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Top Forums UNIX for Dummies Questions & Answers Comparing data list... Post 34679 by TioTony on Wednesday 5th of March 2003 12:46:28 AM
Old 03-05-2003
The '-e' in the 'if' statement checks the current directory to see if the file exists. You do not need to build a data structure containing the 'ls' input. You can simply check the directory directly. In the example, what will happen is it will do the following:

if janfile.tar exists, then print found and exit
if janfile.jar exists, then print found and exit
if jan.rpt.Z exists, then print found and exit

There is no reason to compare 'mylist' against every file in the directory. Suppose you have 1000 file in the directory and you only care if janfile.tar exists. Why would you want to compare it to the other 999 files when you can basically have the program asks if it exists or not without having to iterate through each filename? The for loop is looping through the values of mylist and "asking" if those files exist, it does not care about the other file that may or may not be in that directory. Hope that explains it.
 

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FILE_EXISTS(3)								 1							    FILE_EXISTS(3)

file_exists - Checks whether a file or directory exists

SYNOPSIS
bool file_exists (string $filename) DESCRIPTION
Checks whether a file or directory exists. PARAMETERS
o $filename - Path to the file or directory. On windows, use //computername/share/filename or \computernamesharefilename to check files on network shares. RETURN VALUES
Returns TRUE if the file or directory specified by $filename exists; FALSE otherwise. Note This function will return FALSE for symlinks pointing to non-existing files. Warning This function returns FALSE for files inaccessible due to safe mode restrictions. However these files still can be included if they are located in safe_mode_include_dir. Note The check is done using the real UID/GID instead of the effective one. Note Because PHP's integer type is signed and many platforms use 32bit integers, some filesystem functions may return unexpected results for files which are larger than 2GB. EXAMPLES
Example #1 Testing whether a file exists <?php $filename = '/path/to/foo.txt'; if (file_exists($filename)) { echo "The file $filename exists"; } else { echo "The file $filename does not exist"; } ?> ERRORS
/EXCEPTIONS Upon failure, an E_WARNING is emitted. NOTES
Note The results of this function are cached. See clearstatcache(3) for more details. Tip As of PHP 5.0.0, this function can also be used with some URL wrappers. Refer to "Supported Protocols and Wrappers" to determine which wrappers support stat(3) family of functionality. SEE ALSO
is_readable(3), is_writable(3), is_file(3), file(3). PHP Documentation Group FILE_EXISTS(3)
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