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  • Why does Python Array Module Process Strings and Lists Differently?

    - by Casey
    I'm having trouble understanding the result of the following statements: >>> from array import array >>> array('L',[0xff,0xff,0xff,0xff]) array('L', [255L, 255L, 255L, 255L]) >>> from array import array >>> array('L','\xff\xff\xff\xff') Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: string length not a multiple of item size

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  • Code golf - hex to (raw) binary conversion

    - by Alnitak
    In response to this question asking about hex to (raw) binary conversion, a comment suggested that it could be solved in "5-10 lines of C, or any other language." I'm sure that for (some) scripting languages that could be achieved, and would like to see how. Can we prove that comment true, for C, too? NB: this doesn't mean hex to ASCII binary - specifically the output should be a raw octet stream corresponding to the input ASCII hex. Also, the input parser should skip/ignore white space. edit (by Brian Campbell) May I propose the following rules, for consistency? Feel free to edit or delete these if you don't think these are helpful, but I think that since there has been some discussion of how certain cases should work, some clarification would be helpful. The program must read from stdin and write to stdout (we could also allow reading from and writing to files passed in on the command line, but I can't imagine that would be shorter in any language than stdin and stdout) The program must use only packages included with your base, standard language distribution. In the case of C/C++, this means their respective standard libraries, and not POSIX. The program must compile or run without any special options passed to the compiler or interpreter (so, 'gcc myprog.c' or 'python myprog.py' or 'ruby myprog.rb' are OK, while 'ruby -rscanf myprog.rb' is not allowed; requiring/importing modules counts against your character count). The program should read integer bytes represented by pairs of adjacent hexadecimal digits (upper, lower, or mixed case), optionally separated by whitespace, and write the corresponding bytes to output. Each pair of hexadecimal digits is written with most significant nibble first. The behavior of the program on invalid input (characters besides [a-fA-F \t\r\n], spaces separating the two characters in an individual byte, an odd number of hex digits in the input) is undefined; any behavior (other than actively damaging the user's computer or something) on bad input is acceptable (throwing an error, stopping output, ignoring bad characters, treating a single character as the value of one byte, are all OK) The program may write no additional bytes to output. Code is scored by fewest total bytes in the source file. (Or, if we wanted to be more true to the original challenge, the score would be based on lowest number of lines of code; I would impose an 80 character limit per line in that case, since otherwise you'd get a bunch of ties for 1 line).

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  • write system call to file desciptor ZERO

    - by shadyabhi
    int main ( ) { char C[] = "Hello World"; write(0,C,sizeof(C)); return 0; } In the above program, I am writing to File descriptor ZERO which I suppose by default is STDIN.. Then why I am I getting output at STDOUT? shadyabhi@shadyabhi-desktop:~$ ./a.out Hello Worldshadyabhi@shadyabhi-desktop:~$

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  • SQL: convert backup file from copy format to insert format

    - by takeshin
    I have a PostgreSQL backup made with PHPPgadmin using Export Copy (instead Copy SQL which is actually what I need). File contains entries like this: COPY tablename(id, field) FROM stdin; ... How to convert this file to SQL format? INSERT INTO tablename... I want to use Pgadmin to to import this file using execute SQL command.

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  • python: strip comma end of string

    - by krisdigitx
    how do i strip comma from the end of an string, i tried awk = subprocess.Popen([r"awk", "{print $10}"], stdin=subprocess.PIPE) awk_stdin = awk.communicate(uptime_stdout)[0] print awk_stdin temp = awk_stdin t = temp.strip(",") also tried t = temp.rstrip(","), both don't work.

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  • How do you pipe output from a Ruby script to 'head' without getting a broken pipe error

    - by dan
    I have a simple Ruby script that looks like this require 'csv' while line = STDIN.gets array = CSV.parse_line(line) puts array[2] end But when I try using this script in a Unix pipeline like this, I get 10 lines of output, followed by an error: ruby lib/myscript.rb < data.csv | head 12080450 12080451 12080517 12081046 12081048 12081050 12081051 12081052 12081054 lib/myscript.rb:4:in `write': Broken pipe - <STDOUT> (Errno::EPIPE) Is there a way to write the Ruby script in a way that prevents the broken pipe exception from being raised?

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  • python popen and mysql import

    - by khelll
    I'm doing the following: from subprocess import PIPE from subprocess import Popen file = 'dump.sql.gz' p1 = Popen(["gzip", "-cd" ,file], stdout=PIPE) print "Importing temporary file %s" % file p2 = Popen(["mysql","--default-character-set=utf8", "--user=root" , "--password=something", "--host=localhost", "--port=3306" , 'my_db'],stdin=p1.stdout, stdout=PIPE,stderr=PIPE) err = p1.communicate()[1] if err: print err err = p2.communicate()[1] if err: print err But the db is not being populated. No errors are shown, also I have checked p1.stdout and it has the file contents. Any ideas?

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  • Why does Python array moduel handle strings and lists differently?

    - by Casey
    I'm having trouble understanding the result of the following statements: >>> from array import array >>> array('L',[0xff,0xff,0xff,0xff]) array('L', [255L, 255L, 255L, 255L]) >>> from array import array >>> array('L','\xff\xff\xff\xff') Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: string length not a multiple of item size

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  • Python equivalent of C++ getline()

    - by Arnab Sen Gupta
    In C++ we can enter multiple lines by giving our own choice of delimiting character in the getline() function.. however I am not able to do the same in Python!! it has only raw_input() and sys.stdin.readline() methods that read till I press enter. Is there any way to customize this so that I can specify my own delimiter?

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  • User input without waiting for enter

    - by Hermann Ingjaldsson
    I am trying to make an interactive shell script in perl. The only user input I can find is the following: $name = <STDIN>; print STDOUT "Hello $name\n"; But in this the user must always press enter for the changes to take effect. How can I get the program to proceed immediately after a button has been pressed?

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  • gets (variable)

    - by borlee
    can anyone tell me why gets(abc) works with char[] but not with int? int abc; char name[] = "lolrofl"; printf("Hello %s.\n",name); printf("\n "); fflush(stdin); gets (abc); printf("\n die zahl ist %i.\n",abc); system("Pause"); return(0);

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  • Source From Standard In (Bash on OSX)

    - by yar
    I am trying to do something like this ruby test.rb | source /dev/stdin where test.rb just prints out cd /. There are no errors, but it doesn't do anything either. If I use this: ruby test.rb > /eraseme; source /eraseme it works fine, but I want to avoid the intermediate file.

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  • How to read and write a STL C++ string?

    - by cambr
    #include<string> ... string in; //How do I store a string from stdin to in? // //gets(in) - 16 cannot convert `std::string' to `char*' for argument `1' to //char* gets (char*)' // //scanf("%s",in) also gives some weird error Similarly, how do I write out in to stdout or to a file??

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  • SQL: covert backup file from copy format to insert format

    - by takeshin
    I have a PostgreSQL backup made with PHPPgadmin using Export Copy (instead Copy SQL which is actually what I need). File contains entries like this: COPY tablename(id, field) FROM stdin; ... How to convert this file to SQL format? INSERT INTO tablename... I want to use Pgadmin to to import this file using execute SQL command.

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  • Start two processes and connect them with a pipe in Delphi

    - by Steve
    I need to launch two external programs in my program and connect the STDOUT of the first one to the STDIN of the second program. How can you achieve this in Delphi (RAD Studio 2009, if it matters)? I'm operating in Windows environment. As a commandline command my situation would look something like this: dumpdata.exe | encrypt.exe "mydata.dat"

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  • fgets instructions gets skipped.Why?

    - by nunos
    Whenever I do a scanf before a fgets the fgets instruction gets skipped. I have come accross this issue in C++ and I remember I had to had some instrcution that would clear the stdin buffer or something like that. I suppose there's an equivalent for C. What is it? Thanks.

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  • Exporting an Environment Variable in Ruby

    - by wilhelmtell
    How do I export an environment variable from within a Ruby script to the parent shell? For example, implementing a naïve implementation of the /usr/bin/read utility: #!/usr/bin/ruby varname = ARGV[0] ENV[varname] = STDIN.gets # but have varname exported to the parent process

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  • How do I run an interactive command line Python app inside of Emacs on Win32?

    - by sludge
    If I use M-x shell and run the interactive Python interpreter, Emacs on Windows does not return any IO. When I discovered M-x python-shell, I regained hope. However, instead of running the interactive Python shell, I want to run a specific Python script that features an interactive CLI. (See Python's cmd module for details). Is there a way of launching a Python script in Emacs that is interactive? (stdout, stdin, stderr)

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  • can't read from stream until child exits?

    - by BobTurbo
    OK I have a program that creates two pipes - forks - the child's stdin and stdout are redirected to one end of each pipe - the parent is connected to the other ends of the pipes and tries to read the stream associated with the child's output and print it to the screen (and I will also make it write to the input of the child eventually). The problem is, when the parent tries to fgets the child's output stream, it just stalls and waits until the child dies to fgets and then print the output. If the child doesn't exit, it just waits forever. What is going on? I thought that maybe fgets would block until SOMETHING was in the stream, but not block all the way until the child gives up its file descriptors. Here is the code: #include <stdlib.h> #include <stdio.h> #include <string.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char *argv[]) { FILE* fpin; FILE* fpout; int input_fd[2]; int output_fd[2]; pid_t pid; int status; char input[100]; char output[100]; char *args[] = {"/somepath/someprogram", NULL}; fgets(input, 100, stdin); // the user inputs the program name to exec pipe(input_fd); pipe(output_fd); pid = fork(); if (pid == 0) { close(input_fd[1]); close(output_fd[0]); dup2(input_fd[0], 0); dup2(output_fd[1], 1); input[strlen(input)-1] = '\0'; execvp(input, args); } else { close(input_fd[0]); close(output_fd[1]); fpin = fdopen(input_fd[1], "w"); fpout = fdopen(output_fd[0], "r"); while(!feof(fpout)) { fgets(output, 100, fpout); printf("output: %s\n", output); } } return 0; }

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  • create backup file descriptor?

    - by BobTurbo
    stdinBackup = 4; dup2(0, stdinBackup); Currently I am doing the above to 'backup' stdin so that it can be restored from backup later after it has been redirected somewhere else. I have a feeling that I am doing a lot wrong? (eg arbitrarily assigning 4 is surely not right). Anyone point me in the right direction?

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