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LDIF files

LDIF files -- Converting between Net_LDAP_Entries and LDIF files

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LDIF support was added to Net_LDAP in release 1.1.0a1.

What are LDIF files?

LDIF files are in detail described at RFC 2849. Shortly, they contain directory data in an plain text, human readable kind, much like a SQL file does. However, unlike SQL files LDIF files are mostly data based, not action based. There are two different LDIF file contents, which can be mixed freely - content and change files. The first and most often used one is the LDIF content file:

LDIF files could describe not only the data an entry contains, but also various changes to the entry itself. If such an LDIF file would then be given to a LDAP server, he would interpret those changes instead just importing the data. Note in the example below, that even though LDIF content and LDIF change files could be mixed freely, this is not true for individual entries: a specific entry may be either describing content or changes, but not both.

Error handling when using Net_LDAP_LDIF

Before we can start using Net_LDAP_LDIF we must say some short words about how error handling works. Net_LDAP_LDIF was designed to have mostly the same API as the original PERL Net::LDAP::LDIF has. Because of this, the methods of Net_LDAP_LDIF do not return a Net_LDAP_Error object. You must use the error() method that will return a Net_LDAP_Error object in case of failure or true in case everything was ok. In LDIF reading mode, you can additionally use error_lines() to get knowledge about where in the input file the error occured.

Construction and options

Regardless if you want to read or write a LDIF file, you always have to use the constructor of Net_LDAP_LDIF to initialize your access to the LDIF file. You need to pass at least one parameter to Net_LDAP_LDIF(): the path of the file that should be read or written. You may pass the open mode as second parameter. The possible file open modes are "r" (read), "w" (write, clears the file first) and "a" (append to the end). In case you omit the open mode, read mode is assumed. The third optional parameter is an associative array containing one or several of the following options:

Table 54-1. Possible configuration options

encodeSome DN values in LDIF cannot be written verbatim and have to be encoded in some way. Possible values are: "none", "canonical" and "base64" (RFC default)base64
onerrorWhat should be done on errors? "undef" will let error handling in your hands, in this case you use error() and error_lines() to process errors manually. "die" aborts the script printing the error - this is sometimes useful for CLI scripts. "warn" just prints out the error but continues like "undef" would.undef
changeTurning this to "1" (true) will tell Net_LDAP_LDIF to write change sets instead of content files.false
lowercaseSet this to true to convert attribute names to lowercase when writing.0
sortIf true, sort attribute names when writing entries according to the rule: objectclass first then all other attributes alphabetically sorted by attribute name0
versionSet the LDIF version to write to the resulting LDIF file. According to RFC 2849 currently the only legal value for this option is 1 currently.1
wrap Number of columns where output line wrapping shall occur. Setting it to 40 or lower inhibits wrapping. Useful for better human readability of the resulting file.78
For advanced users: instead of passing a file path, you also may pass an already initialized file handle. In this case, the mode parameter will be ignored. You may use this, if you want to mix LDIF content and LDIF change mode by using two Net_LDAP_LDIF instances to write to the same filehandle, but it could be very useful in other cases too. To initialize the second instance of Net_LDAP_LDIF, you can use handle() to get the filehandle from the first instance.

Reading a LDIF file into Net_LDAP_Entry-objects

One of the two modes how Net_LDAP_LDIF can be used is to read a LDIF file and parse its contents into an array of Net_LDAP_Entry objects. This is done using the read_entry()-method which will return the next entry. If you want to fetch all entries, you use the eof() to detect the end of the input file:

Writing Net_LDAP_Entry objects to a LDIF content file

Writing an LDIF file is very easy too. Just pass the entries you want to have written to the write_entry()-method. Beware, that if you have opened the file in "w" write mode this will clear any previous data of that file. Use "a" (append) if you just want add data.

Writing Net_LDAP_Entry objects to a LDIF change file

The process of writing changes is exactly the same like writing entry contents. However there are two differences: Firstly you need to pass the "changes" option and secondly, the entries you want to write need changes. Entries not containing changes will silently be ignored since there is nothing to write.

Fetching LDIF data

Sometimes you are interested in the lines inside the LDIF file. For those cases you can use the current_lines() and next_lines() methods. They work in the current context, which may be confusing: current_lines() will always return the lines that have built up the current Net_LDAP_Entry object when called current_entry() after read_entry() has been called. next_lines() will always return the lines, that will build up the next entry from the current point of view, meaning "relative to the entry that was just been read". However, you can override this by activating the "force" parameter of next_lines() which allows you to loop over all entries. current_entry() behaves exactly like current_lines().

If you think, that the lines you have read would be better in form of an Net_LDAP_Entry object, use the parseLines() method to parse those lines into an entry. This is a good way if you need just a few specific entries of a large LDIF file.

Example 54-7. Reading LDIF lines

// open some LDIF file for reading
// (error checking code is ommitted in this example for
//  better readability - in production, test for errors!)
$ldif = new Net_LDAP_LDIF('somefile.ldif', 'r');

// since nothing has been read until now, this will
// return an empty array
$empty_array = $ldif->current_lines();

// so let's read the first entries data
$first_entry_lines = $ldif->next_lines();

// if we call it again, we will not read ahead to the
// second entry - we again read the first one!
$first_entry_lines_again = $ldif->next_lines();

// If we call current_lines() now, we haven't read ahead
// like we learned from the last statement.
$empty_array_again = $ldif->current_lines();

// If we want to shift, we must use
// the read_entry() method, which will read ahead.
$first_entry = $ldif->read_entry();

// Now, current_lines() returns the lines of the
// first entry and next_lines() the lines of the second:
$first_entry_lines  = $ldif->current_lines();
$second_entry_lines = $ldif->next_lines();

// There is another way to shift the lines which is faster if
// you are just interested in the LDIFs content - you
// need to pass the "force" parameter to next_lines():
$third_entry_lines  = $ldif->next_lines(true);
$fourth_entry_lines = $ldif->next_lines(true);
$fifth_entry_lines  = $ldif->next_lines(true);

// If you want to convert the lines to an Net_LDAP_Entry,
// you may do so anytime by using parseLines()
$fourth_entry = $ldif->parseLines($fourth_entry_lines);

// Since we shifted manually only the lines,
// current_lines() will return the lines that built up the
// last (e.g. the first entry) Net_LDAP_Entry object:
$first_entry_lines  = $ldif->current_lines();

// If we decide to read the next entry, we can do that:
$sixth_entry = $ldif->read_entry();

// current_lines() is shifted now:
$sixth_entry_lines = $ldif->current_lines();

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