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  • How to handle inputs in a C shell program during exec

    - by hits_lucky
    I am currently writing my own shell program. This simple shell can just execute commands. When executing commands like vi or calc which require input from the terminal , the command is getting executed and is waiting for the input from the user. But I am unable to give any input on the screen. How should the input be handled during the fork and exec. Here is the piece of code which is executing commands: if((pid = fork()) < 0) { perror("Fork failed"); exit(errno); } if(pid == 0) { // Child process if(execvp(arguments[0], arguments) == -1) { child_status = errno; switch(child_status) { case ENOENT: printf(" command not found \n"); break; } exit(errno); } } else { // parent process int wait_stat; if(waitpid(pid , &wait_stat, WNOHANG) == -1) { printf(" waitpid failed \n"); return; } } } ~ Thanks,

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  • Parsing line with delimiter in Python

    - by neversaint
    I have lines of data which I want to parse. The data looks like this: a score=216 expect=1.05e-06 a score=180 expect=0.0394 What I want to do is to have a subroutine that parse them and return 2 values (score and expect) for each line. However this function of mine doesn't seem to work: def scoreEvalFromMaf(mafLines): for word in mafLines[0]: if word.startswith("score="): theScore = word.split('=')[1] theEval = word.split('=')[2] return [theScore, theEval] raise Exception("encountered an alignment without a score") Please advice what's the right way to do it?

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  • phpMyAdmin Cron to Delete Temporary Files

    - by JoeC
    I have a folder on my hosting which I periodically upload something to - /public_html/uploads - and I'd like to set up a cronjob through phpMyAdmin to empty it out on a regular basis. The current cron I have in pMA is find /public_html/uploads -maxdepth 1 -ctime 1 -exec rm -f {} \; (Ignore the fact that it's running every minute for now, it's so I can test it :) ) I know very little about what this command is actually doing, but it looks like "not very much". Can anyone help me fix it? :) Thanks.

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  • In a process using lots of memory, how can I spawn a shell without a memory-hungry fork()?

    - by kdt
    On an embedded platform (with no swap partition), I have an application whose main process occupies most of the available physical memory. The problem is that I want to launch an external shell script from my application, but using fork() requires that there be enough memory for 2x my original process before the child process (which will ultimately execl itself to something much smaller) can be created. So is there any way to invoke a shell script from a C program without incurring the memory overhead of a fork()? I've considered workarounds such as having a secondary smaller process which is responsible for creating shells, or having a "watcher" script which I signal by touching a file or somesuch, but I'd much rather have something simpler.

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  • join 3 files by first Column with awk ?

    - by noinflection
    i have three similar files, they are all like this: File A ID1 Value1a ID2 Value2a . . . IDN Value2n and i want an output like this Output ID1 Value1a Value1b Value1c ID2 Value2a Value2b Value2c ..... IDN ValueNa ValueNb ValueNc Looking to the first line, i want value1A to be the value of id1 in fileA, value1B the value of id1 in fileB, and so on which each field and each line. I thougth it like a sql join. I've tried several things but none of them where even close.

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  • Setting multiple jars in java classpath

    - by Chris Serra
    Is there a way to include all the jar files within a directory in the classpath? I'm trying java -classpath lib/*.jar:. my.package.Program and it is not able to find class files that are certainly in those jars. Do I need to add each jar file to the classpath separately?

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  • appending text to all files that starts with a string

    - by learner135
    How do I append a string to all the files in a directory that starts with a particular string? I tried, cat mysig >> F* But instead of appending contents of mysig to all files starting with F, it creates a file named "F*". Obviously wildcard doesn't seem to work. Any alternatives? Thanks in advance. Edit: Also how do I delete this newly created file "F*" safely?. Using rm F* would delete all the files starting with F which I wouldn't want.

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  • How to map UID to user name using Perl library functions?

    - by Mike
    I'm looking for a way of mapping a uid (unique number representing a system user) to a user name using Perl. Please don't suggest greping /etc/passwd :) Edit As a clarification, I wasn't looking for a solution that involved reading /etc/passwd explicitly. I realize that under the hood any solution would end up doing this, but I was searching for a library function to do it for me.

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  • Different search paths for tclsh

    - by user364128
    Hi: Any one knows how can I invoke the tclsh in the TCL code due to different paths to tclsh in various platforms (Linux, SUN) ? For example in SUN: !/usr/bin/sun/tclsh in Linux: !/usr/bin/linux/tclsh How can I use the same TCL code and execute it in the above two paths ?

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  • arbitrary input from stdin to shell

    - by python_noob
    So I have this existing command that accepts a single argument, but I need something that accepts the argument over stdin instead. A shell script wrapper like the following works, but as I will be allowing untrusted users to pass arbitrary strings on stdin, I'm wondering if there's potential for someone to execute arbitary commands on the shell. #!/bin/sh $CMD "`cat`" Obviously if $CMD has a vulnerability in the way it processes the argument there's nothing I can do, so I'm concerned stuff like this: Somehow allow the user to escape the double quotes and pass input into argument #2 of $CMD Somehow cause another arbitary command to run

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  • Bash scripting - Iterating through "variable" variable names for a list of associative arrays

    - by user1550254
    I've got a variable list of associative arrays that I want to iterate through and retrieve their key/value pairs. I iterate through a single associative array by listing all its keys and getting the values, ie. for key in "${!queue1[@]}" do echo "key : $key" echo "value : ${queue1[$key]}" done The tricky part is that the names of the associative arrays are variable variables, e.g. given count = 5, the associative arrays would be named queue1, queue2, queue3, queue4, queue5. I'm trying to replace the sequence above based on a count, but so far every combination of parentheses and eval has not yielded much more then bad substitution errors. e.g below: for count in {1,2,3,4,5} do for key in "${!queue${count}[@]}" do echo "key : $key" echo "value : ${queue${count}[$key]}" done done Help would be very much appreciated!

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  • How to get proper alignment when printing to file

    - by user1067334
    I have this Structure the elements of which that I need to write in a text file struct Stage3ADisplay { int nSlot; char *Item; char *Type; int nIndex; unsigned char attributesMD[17]; //the last character is \0 unsigned char contentsMD[17]; //only for regular files - //the last character is \0 }; buffer = malloc(sizeof(Stage3ADisplayVar[nIterator]->nSlot) + sizeof(Stage3ADisplayVar[nIterator]->Item) + sizeof(Stage3ADisplayVar[nIterator]->Type) + sizeof(Stage3ADisplayVar[nIterator]->nIndex) + sizeof(Stage3ADisplayVar[nIterator]->attributesMD) + sizeof(Stage3ADisplayVar[nIterator]->contentsMD) + 1); sprintf (buffer,"%d %s %s %d %x %x",Stage3ADisplayVar[nIterator]->nSlot, Stage3ADisplayVar[nIterator]->Item,Stage3ADisplayVar[nIterator]->Type,Stage3ADisplayVar[nIterator]->nIndex,Stage3ADisplayVar[nIterator]->attributesMD,Stage3ADisplayVar[nIterator]->contentsMD); How do I make sure the rows in the file are properly aligned. Thank you.

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  • Stacking standard output of `su`

    - by Kristopher Ives
    I've got some code that I wrote that uses a combination of bash and PHP command line scripting. The script is ran as root and then uses su to become various uses. I start a session like this: $result = `su SomeUser ./dothis.php` Here ./dothis.php is a script that may generate some output being stored in $result, but the problem is that there is usually output that doesn't get caught and makes it hard for me to read my script output. How can I make sure that the output is being captured within this su stacking?

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  • how to check if a path is actual or symbolic link

    - by hits_lucky
    Hi, I am writing my own shell program. I am currently implementing the cd command using chdir. I want to implement the cd with the below options : -P Do not follow symbolic links -L Follow symbolic links (default) My query is that , when a given path is entered on the shell how to figure out if the path is a symbolic link or an absolute path progamatically? Thanks

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  • what does '-' stand for in bash?

    - by trybeingarun
    Hi, What exactly are the uses of '-' in bash? I know they can be used for 1. cd - # to take you to the old 'present working directory' 2. some stream generating command | vim - # somehow vim gets the text. My question is what exactly is - in bash? In what other contexts can I use it? Regards Arun

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  • Which Java Service or Daemon framework would you recommend?

    - by blwy10
    I have encountered many different ways to turn a Java program into a Windows Service or a *nix daemon, such as Java Service Wrapper, Apache Commons Daemon, and so on. Barring licensing concerns (such as JSW's GPL or pay dual-license), and more advanced features, which one would you recommend? All I intend to do is convert a simple Java program into a service; I don't need anything fancy, just something that runs as a service or a daemon, so I can start it or stop it in the service manager, or it runs for the lifetime of my *nix uptime. EDIT: I've decided to make this community wiki. I didn't start this question with an intention to find an answer for a problem I really had. I was just doing some reading and researching and chanced upon this question, so I was looking for recommendations and the like. Sorry for not doing this sooner or doing this at first. I didn't know what community wiki was for when I first started, and I completely forgot about this question until now. Many thanks for the answers!

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