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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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  • How to warn for the use of unset variables in a korn shell script

    - by Lepu
    Is there any way to throw errors or warnings in a korn shell script to prevent the use of unset variables ? Let's assume I have a temporary folder that I want to remove. TEMP_FILES_DIR='/app/myapp/tmp' rm -Rf $TEMP_FILE_DIR #notice the misspelling How to prevent this kind of mistakes before they actually happen? I know the script should check for file existence and empty string before attempting to remove, this is just a silly example to illustrate a mistake that could have been avoided with some warnings. I don't know if this feature exists in ksh. If it does exist, how do you turn it on?

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  • How do I use Perl to parse the output of the sqlplus command?

    - by benjamin button
    I have an SQL file which will give me an output like below: 10|1 10|2 10|3 11|2 11|4 . . . I am using this in a Perl script like below: my @tmp_cycledef = `sqlplus -s $connstr \@DLCycleState.sql`; after this above statement, since @tmp_cycledef has all the output of the SQL query, I want to show the output as: 10 1,2,3 11 2,4 How could I do this using Perl?

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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 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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  • 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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  • Why is sys+user > real in "time command"?

    - by shadyabhi
    I have a program that uses pthread library to do the matrix multiplication of 500x500 matrix. Each thread calculates 50 rows of the matrix. When I run tiem command:- shadyabhi@shadyabhi-desktop:~$ time ./a.out real 0m0.383s user 0m0.810s sys 0m0.000s shadyabhi@shadyabhi-desktop:~$ How come sys+user is greater than real time?

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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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  • 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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