linux - While read line is very slow -

-

i want create thumbs large list of images. problem is, appears while read line slow large lists. 1 solution can think of create files contain max 500 lines , read them 1 one. there smart solution problem?

while read line;   if [ -e "$line" ] && [ ! -z "$line" ];               ...   fi } done <<< "$imageslist"

your problem you're using here string read in these lines via <<<. slow if here string large.

if $imgagelist file, can file redirect , lot faster:

while read line     if [ -e "$line" -a ! -z "$line" ]            ...     fi done < "$imageslist_file"  # redirect file.

you might able this:

echo "$imageslist" | while read line         if [ -e "$line" -a ! -z "$line" ]            ...     fi done

but, worried overloading command line. in linux/unix systems, defined in /usr/include/sys/syslimits.h or /usr/include/syslimits.h. it's 1024 * 256 on system or 262,144 bytes. sounds lot, can deceptive. file names can quite long -- if include directory path in them. long enough pass when you're testing, fail when really, depending upon work. and. fails silently. never know last few file names dropped off.

your best bet create file list of image names instead of loading them in environment variable.


Comments

Post a Comment

Popular posts from this blog

c# - How Configure Devart dotConnect for SQLite Code First? -

-
can configure following sample code ? when run following code, error : no entity framework provider found ado.net provider invariant name 'devart.data.sqlite' setting in machine.config <system.data> <dbproviderfactories> <add name="dotconnect sqlite" invariant="devart.data.sqlite" description="devart dotconnect sqlite" type="devart.data.sqlite.sqliteproviderfactory, devart.data.sqlite, version=4.6.287.0, culture=neutral, publickeytoken=09af7300eec23701" /> </dbproviderfactories> </system.data> after add below block code in app.config <?xml version="1.0"?> <configuration>   <configsections> <!-- more information on entity framework configuration, visit http://go.microsoft.com/fwlink/?linkid=237468 --> <section name="entityframework" type="system.data.entity.internal.configfile.entityframeworksection, entit...
Read more

java - Copying object fields -

-
what best way of copying classes when need have 2 independent variables? have simple class: public class myclass { boolean = false; string b= "not empty"; } do need make method : assign(myclass data ) { a= data.a; b= data.b; } is there automatic method copy (duplicate) objects in java? do need make method : pretty close. instead of making method, should make constructor. such constructors called copy constructor , , create them this: myclass(myclass data) { = data.a; b = data.b; } and create copy of instance, use constructor this: myclass obj1 = new myclass(); myclass obj2 = new myclass(obj1); copy constructor can tedious : using copy constructor create deep-copy can tedious, when class has mutable fields. in case, assignment create copy of reference, , not object itself. have create copy of fields (if want deep copy). can go recursive. a better way create deep copy serialize , deserialize object. why not use clone()? ...
Read more

c++ - Clear the memory after returning a vector in a function -

-
i have function processes , stores lot of data in , returns results vector of class. amount of data stored in function tremendous , want clear storage memory of function after finished job. necessary (does function automatically clear memory) or should clear memory function? update: vector<customers> process(char* const *filename, vector<int> id) { vector<customers> list_of_customers; (perform actions) return list_of_customers; } variables defined locally within function automatically released @ end of function scope. destructors objects called, should free memory allocated objects (if objects coded correctly). example of such object std::vector . anything you've allocated new must have corresponding delete release storage. try avoid doing own allocation , use raii instead, i.e. containers or smart pointers.
Read more