What's the story behind our massive repitition of ./foo and cd ... Where do these two . and .. come from? Where could they be seen as a way of navigating a file system tree for the first time?
Excerpt from an interview with Ken Thompson (9-6-89):
Every time we made a directory, by
convention we put it in another
directory called directory -
directory, which was dd. Its name was
dd and that all the users directories
and in fact most other directories,
users maintain their own directory
systems, had pointers back to dd, and
dd got shortened into ‘dot-dot,’ and
dd was for directory-directory.
I'm sorry I can't answer properly, but I can recommend these links:
The Evolution of the Unix Time-sharing System and
A Brief history of the BSD Fast File System
for some interesting historical notes on early file systems and their use.
Other than that, the earliest reference I've found is the 1974 paper "The UNIX Time-Sharing System" by Dennis Ritchie and Ken Thompson. The precursor of UNIX, Multics, also had hierarchical file systems and the notion of relative paths, but according to "Introduction to MULTICS" it used another notation for that.
I believe it was invented by Dennis Ritchie at Bell Labs in the early years of Unix.
Related
I have heard a lot of people saying "Jupyter" with "py" as in Python, while others say "Jupyter", with "py" as in the name of the planet.
So, what is the most correct form?
Fortunately, there are many videos and podcasts with Fernando Pérez and Brian Granger, core developers of IPython/Project Jupyter and we can easily check them. They say Jupyter with "py" as in the name of the planet.
Here is an example of Fernando Perez talking about Jupyter, in PLOTCON 2016: Fernando Perez, The architecture of Jupyter.
The following is from a school assignment.
The question asks
"What command enables you to find all empty files in your source
directory."
My answer; find -size 0 However, my instructor says that my answer is incorrect. The only hint (Regarding the entirety of the assignment) he gives me is "...minor errors such as missing a file name or outputting too much information" I was thinking, perhaps I should include the source directory within my find command.
I've been trying to figure this out for the past few hours. I've referenced my textbook and according to that I should be correct.
There's some other questions I'm having similar issues with. I've wracked my brain with this for hours. I just don't know. I don't understand what I'm doing wrong.
Since your assignment was to find all empty files in your source directory, the following command will do exactly what you want:
find . -size 0
Notice the dot (.) to tell the command to search in the current folder.
For other folders, you replace the "dot" with the folder you want.
For the AFP entry Dijkstra's Shortest Path Algorithm, both the proof outline and proof document were nonexistent *. Unfortunately, I did not find an IsaMakefile either to build those documents locally. What is the best way to get those documents?
Another question, as the Dijkstra.thy depends on a lot of other theories, is there a way to load everything faster?
*) It is fixed now.
(There seems to be something broken at AFP right now, please tell the editors about it.)
In general, you can download the sources of AFP entries and produce the documents yourself like this:
Get and unpack all AFP sources -- downloading separate entries is offered as well, but then you have to disentangle dependencies manually.
Invoke isabelle build like this:
isabelle build -d afp-2013-03-02 -o document=pdf -v Dijkstra_Shortest_Path
Here afp-2013-03-02 is the directory that was obtained by unpacking the current AFP sources.
See also the Isabelle System manual about "Isabelle sessions and build management", which is all new in Isabelle2013.
See isabelle build -b there to make things load faster, by producing persistent heap images from sessions.
The links in the AFP entry were indeed broken and should now be fixed again, sorry about that.
As Makarius writes, the AFP new uses Isabelle's new build system, i.e. has a ROOT file for each entry that can be used to check the associated theories and build the document.
Makarius' answer is pretty much the official way to do it, although I would additionally recommend setting up the AFP as a component. This gives you the following steps:
Download the AFP to e.g. ~/afp
Set it up as component e.g. by adding ~/afp to ~/.isabelle/Isabelle2013/components (see also AFP as a component)
build the entry with
isabelle afp_build Dijkstra_Shortest_Path
You can also have jEdit build the heap image for you. If the AFP is setup as a component (see the other answers for that), just start jEdit with
isabelle jedit -d '$AFP' -l Dijkstra_Shortest_Path
and jEdit will select Dijkstra_Shortest_Path as base logic and (re)build it if necessary.
If you make regular use of the AFP, it might be useful to add the AFP path by default. For this, create a file ROOTS in $ISABELLE_HOME_USER with the line $AFP in it (or add this line, if the file already exists).
I've found this dictionary by William Whitaker on the Internet and I like its parsing capabilities. But the output doesn't fit for me.
The issue (challenge for me):
Given an input form such as "audiam", the program returns the following output (plain text):
audi.am V 4 1 PRES ACTIVE SUB 1 S
audi.am V 4 1 FUT ACTIVE IND 1 S
audio, audire, audivi, auditus V (4th) [XXXAO]
hear, listen, accept, agree with; obey; harken, pay attention; be able to hear;
But I just want to receive the following text output (same input: audiam):
audiam=audio, audire, audivi, auditus
That is:
InputWord=Dictionary_Forms
So some pieces of information are needless for me.
How can I change the output of this program by modifying the Ada code?
I don't have any Ada knowledge, but I know Delphi/Pascal so it's quite easy to understand the code, isn't it? So the parts causing the text output seem to be the TEXT_IO.PUT(...) statements, right? They're all called in list_package.adb so this is probably the source file to look at.
What has to be changed in particular?
The full Ada 95 source code of this program is available on this page.
I hope some of you are able to understand Ada 95 code. Thank you very much in advance!
My compiling problems:
For use on a windows machine, I downloaded MinGW and tried to compile the source files using "MinGW Shell". But this was my input and the shell's reponse:
Compiling with the latest Cygwin version:
When I compile the program using the latest version of Cygwin, there is no error message:
There is even an .exe file which is created. Its size is 1.6 MB (1,682,616 bytes). But when I open it, it closes right away. What has gone wrong?
William Whitaker's Words is a handy tool. You may be able to find a version already built for your platform. I've not changed the code, but you can alter some things using various parameters. It's even hosted online. If you get an Ada compiler, I've included the last Makefile I used. It's a little thin on abstraction, but it includes the essential steps to compile the program and utilities, along with the steps to build the dictionaries.
TARG = words
ARGS = -O
$(TARG): *.ad[bs]
gnatmake $(TARG) $(ARGS)
all: $(TARG)
gnatmake makedict $(ARGS)
gnatmake makeinfl $(ARGS)
gnatmake makestem $(ARGS)
gnatmake makeefil $(ARGS)
#echo Please make the dicitionary
#echo ./makedict DICTLINE.GEN
#echo ./makestem STEMLIST.GEN
#echo ./makeefil EWDSLIST.GEN
#echo ./makeinfl INFLECTS.GEN
debug:
gnatmake -g $(TARG)
clean:
rm -f *.o *.ali b~* core
cleaner: clean
rm -f *.s makedict makeinfl makestem makeefil
cleanest: cleaner
rm -f $(TARG)
Addendum: One approach is to use gcc 4.4.3 on Ubuntu 10.04 with the updated Makefile above. For convenience, I used VirtualBox to host the linux instance.
$ gcc --version
gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Here's a quick test using the title of my second favorite passage from Catulli Carmina.
$ ./words odi et amo
odi V 6 1 PRES ACTIVE IMP 2 S
odeo, odire, odivi(ii), - V TRANS [EXXCW] Later
od.i V 4 1 PRES ACTIVE IMP 2 S
odio, odire, odivi, - V (4th) TRANS [FXXCF] Medieval
hate; dislike; be disinclined/reluctant/adverse to; (usu. PREFDEF);
odi N 2 4 GEN S N Early
odium, odi(i) N (2nd) N [XXXAO]
hate/hatred/dislike/antipathy; odium, unpopularity; boredom/impatience;
hatred (manifested by/towards group), hostility; object of hate/odium;
od.i V 3 1 PERF ACTIVE IND 1 S
odi, odisse, osus V (3rd) PERFDEF [XXXBX]
hate (PERF form, PRES force), dislike; be disinclined/reluctant/adverse to;
et CONJ
et CONJ [XXXAX]
and, and even; also, even; (et ... et = both ... and);
am.o V 1 1 PRES ACTIVE IND 1 S
amo, amare, amavi, amatus V (1st) [XXXAO]
love, like; fall in love with; be fond of; have a tendency to;
Addendum: Once you've got it running, the problem of modifying it remains. A grep for Put_Line\( shows 629 hits; most are in line_stuff and list*. That's where I'd start. As you are learning Ada, there are several good tutorials here.
As much as I like Ada and would encourage you to learn the minimal amount it would require to hack it the way you want...
Really, you are asking for a simple data filter, which it would be quite easy to accomplish by piping your output to awk. If you are running on any flavor of Linux you have awk already (and really should learn to use it). If you are on Windows, you can get awk and all sorts of other useful goodies from MinGW, which is one of the places you'd need to go to get an Ada compiler anyway.
If you do want a Windows Ada compiler, I'd suggest getting GNAT/GCC from there. The two other flavors available, GNAT/GPL and GNAT/PRO are available from AdaCore (the maintainers). However, GNAT/PRO must be purchased and GNAT/GPL renders distributions of any program compiled using it GPL. You might not mind the GPL applying to your program I suppose, but I'm guessing this isn't a serious enough need to spring for commercial support.
If you are on Linux, the GNAT Ada compiler should be available with GCC as an option (if not installed by default). The same two other options from AdaCore are available there too of course, if you like.
Well, you asked about learning Ada. Really, if you are familiar with other compiled procedural languages (eg: C/C++, Java, Pascal, Modula-2, etc.) you shouldn't have too much trouble picking it up. This question covers Ada books. For myself, I generally just use the official LRM as a reference. Unlike most languages, Ada has an internationally standardized Language Reference Manual that is available online for free. It is also quite readable, as such things go.
About compiling: you can use GNAT. It supports Ada83, Ada95, and Ada05. To tell it to use Ada95, use the -gnat95 switch.
You can get it on http://libre.adacore.com/
I'm looking for the equivalent of right clicking on the drive in windows and seeing the disk space used and remaining info.
Look for the commands du (disk usage) and df (disk free)
Use the df command:
df -h
df -g .
Option g for Size in GBs Block and . for current working directory.
I love doing du -sh * | sort -nr | less to sort by the largest files first
If you want to see how much space each folder ocuppes:
du -sh *
s – summarize
h – human readable
* – list of folders
Note: The original question was answered already, but I would just like to expand on it with some extras that are relevant to the topic.
Your AIX installation would first be put into volume groups. This is done upon installation.
It will first create rootvg (as in root volume group). This is kinda like your actual hard drive mapped.
This would be equivalent to Disc Management in Windows. AIX wont use up all of that space for its file systems like we tend to do it in consumer Windows machines. Instead there will be a good bit of unallocated space.
To check how much space your rootvg would have you use the following command.
lsvg rootvg
That would stand for list volume group rootvg. This will give you information like the size of physical partitions (PP), Total PPs assigned to the volume group, Free PPs in the volume group, etc. Regardless, the output should be fairly comprehensive.
Next thing you may be interested in, is the file systems on the volume group. Each file system would have certain amount of space given within the volume group it belongs to.
To check what file systems you got on your volume group you use the following command.
lsvgfs rootvg
As in list volume group file systems for rootvg.
You can check how much space each file system has using the following command.
df
I personally like to refine it with flags like -m and -g (in megabytes and gigabytes respectively)
If you have free space available in your volume group, you can assign it to your file systems using the following command.
chfs -a size=+1G /home
As in change file system attribute size by adding 1 G where file system is /home. use man chfs for more instructions. This is a powerful tool. This example is for adjusting size, however you can do more with this command than that.
Sources:
http://www.ibm.com/developerworks/aix/library/au-rootvg/
+ My own experience working with AIX.
All these answers are superficially correct. However, the proper answer is
apropos disk # And pray your admin maintains the whatis database
because asking questions the answers of which lay at your fingertips in the manual wastes everybody's time.
su -sm ./*
You can see every file and folder size (-sm=Mb ; -sk=Kb) in the current directory like a list. This way runs in all Unix/Linux environment.
du -sm * => RULLLLLEZ
df -tk
for Disk Free size in 1024 byte blocks