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  • Print a file skipping X lines in Bash

    - by Eduardo
    Hi I have a very long file which I want to print but skipping the first 1e6 lines for example. I look into the cat man page but I did not see nay option to do this. I am looking for a command to do this or a simple bash program. I know how to do it using a program in C but I want to do it using the common commands. Any way to do it? Thanks a lot in advance..

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  • Why does mmap() fail with ENOMEM on a 1TB sparse file?

    - by metadaddy
    I've been working with large sparse files on openSUSE 11.2 x86_64. When I try to mmap() a 1TB sparse file, it fails with ENOMEM. I would have thought that the 64 bit address space would be adequate to map in a terabyte, but it seems not. Experimenting further, a 1GB file works fine, but a 2GB file (and anything bigger) fails. I'm guessing there might be a setting somewhere to tweak, but an extensive search turns up nothing. Here's some sample code that shows the problem - any clues? #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char *argv[]) { char * filename = argv[1]; int fd; off_t size = 1UL << 40; // 30 == 1GB, 40 == 1TB fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666); ftruncate(fd, size); printf("Created %ld byte sparse file\n", size); char * buffer = (char *)mmap(NULL, (size_t)size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if ( buffer == MAP_FAILED ) { perror("mmap"); exit(1); } printf("Done mmap - returned 0x0%lx\n", (unsigned long)buffer); strcpy( buffer, "cafebabe" ); printf("Wrote to start\n"); strcpy( buffer + (size - 9), "deadbeef" ); printf("Wrote to end\n"); if ( munmap(buffer, (size_t)size) < 0 ) { perror("munmap"); exit(1); } close(fd); return 0; }

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  • symlink files newer than X age, then later remove symlink once file ages?

    - by bleomycin
    Hello everyone, i have a large number of files/folders coming in each day that are being sorted automatically to a wide variety of folders. I'm looking for a way to automatically find these files/folders and create symlinks to them all within an "incoming" folder. Searching for file age should be sufficient for finding the files, however searching for age and owner would be ideal. Then once the files/folders being linked to reach a certain age, say 5 days, remove the symlinks to them automatically from the "incoming" folder. Is this possible to do with a simple shell or python script that can be run with cron? Thanks!

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  • How to replicate Google "Hangouts On Air" stream combining functionality?

    - by Rob Olmos
    I've been researching this one for quite a bit but haven't found any solid leads. I have a Wowza/Flash app with video chatroom functionality and would like to combine the streams server-side into one video/audio stream in order to be sent to a live Youtube channel. I've found a couple projects such as jMixer and some helpful keywords such as "vision mixer" to help with my search but looking for any previous experience or new ideas. The other option is building something like it myself with a commercial video decoding/encoding library to raw frames, stitching the frames together, then encoding it. I was originally going down this route but put project on hold. What are some ideas, keywords, or existing software (open source preferred) to take those live streams and combine them into one in real-time? Or is coding it myself the required route? Thanks!

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  • Random password variable disappears

    - by snaken
    Hi, I'm using the following to generate a random password in a shell script: DBPASS=</dev/urandom tr -dc A-Za-z0-9| (head -c $1 > /dev/null 2>&1 || head -c 8) When i run this in a file on its own like this: #!/bin/sh DBPASS=</dev/urandom tr -dc A-Za-z0-9| (head -c $1 > /dev/null 2>&1 || head -c 8) echo $DBPASS A password is echoed. When i incorporate it into a larger script though the variable never seems to get created for some reason, so for example this doesn't work: DBPASS=</dev/urandom tr -dc A-Za-z0-9| (head -c $1 > /dev/null 2>&1 || head -c 8) sed -i s/oldpass/$DBPASS/ mysql_connect.php If i manually set the variable though everything is fine.. can anyone see why?

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  • If a command line program is unsure of stdout's encoding, what encoding should it output?

    - by mackstann
    I have a command line program written in Python, and when I pipe it through another program on the command line, sys.stdout.encoding is None. This makes sense, I suppose -- the output could be another program, or a file you're redirecting it into, or whatever, and it doesn't know what encoding is desired. But neither do I! This program will be used by many different people (humor me) in different ways. Should I play it safe and output only ascii (replacing non-ascii chars with question marks)? Or should I output UTF-8, since it's so widespread these days?

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  • how to delete a line from file using awk filtered by some string

    - by embedded
    I have a file delimited by space. I need to write an awk command that receives a host name argument and it should replace the host name if it already defined in the file. It must be a full match not partially - if the file contains this host name: localhost searching for "ho" will fail and it will be added to the end of the file. another option is a delete: again awk receives host name argument and it should remove it from the file if exists. This is what I have so far: (It needs some enhancements) if [ "$DELETE_FLAG" == "" ]; then # In this case the entry should be added or updated # if clause deals with updating an existing entry # END clause deals with adding a new entry awk -F"[ ]" "BEGIN { found = 0;} \ { \ if ($2 == $HOST_NAME) { \ print \"$IP_ADDRESS $HOST_NAME\"; \ found = 1; \ } else { \ print \$0; \ } \ } \ END { \ if (found == 0) { \ print \"$IP_ADDRESS $HOST_NAME\"; } \ } " \ /etc/hosts > /etc/temp_hosts else # Delete an existing entry awk -F'[ ]' '{if($2 != $HOST_NAME) { print $0} }' /etc/hosts > /etc/temp_hosts fi Thanks

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  • Bash:Redirection Halts

    - by user365828
    I have a command e.g. ls-l file.txt When there is insufficient space on my drive, the above command just stalls waiting for something to happen. Does anyone know about a code that I could write enabling me to display a message about the lack of space on my drive? E.g. could I use IPC or do you have any other ideas? Thanks in advance.

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  • Bash intercepting wildcard in script

    - by MrRoth
    I am using Bash script to read line by line from a text file, which has special characters in it (regular expression). When I use echo "${SOME_VAR}" it does not display the text as is. I am familiar with Prevent * to be expanded in the bash script. How can I display and use the text as is? UPDATE The text (TSV) file holds tuples similar to (the last entry is a psql query) bathroom bathroom select name from photos where name ~* '\mbathroom((s)?|(''s)?)\M'; I am reading the CSV as follows: tail -n+2 text.file | while IFS=$'\t' read x y z do echo "${z}" done which gives the output select name from photos where name ~* 'mbathroom((s)?|(''s)?)M'); note that the '\' is missing

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  • How to remove strings from a compiled binary (.so)

    - by Stéphane
    How do I remove strings from / obfuscate a compiled binary? The goal is to avoid having people read the names of the functions/methods inside. It is a dynamic library (.so) compiled from C++ code for Android with the NDK tools (includes GCC) I compile with -O3 and already use arm-eabi-gcc -g mylib.so to remove debugging symbols, but when I do strings mylib.so all the names of the functions/methods are still readable.

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  • TERM environment variable not set

    - by rahkarp
    I'm using python to develop an app and want to view running processes.The code txt = commands.getoutput("top -d 1") print txt gives an error "TERM Environment Variable not set" Can someone tell me what this means and how to solve this

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  • Notify via email if something wrong got happened in the shell script

    - by Nevzz03
    fileexist=0 for i in $( ls /data/read-only/clv/daily/Finished-HADOOP_EXPORT_&processDate#.done); do mv /data/read-only/clv/daily/Finished-HADOOP_EXPORT_&processDate#.done /data/read-only/clv/daily/archieve-wip/ fileexist=1 done --some other script below Above is the shell script I have in which in the for loop, I am moving some files. I want to notify myself via email if something wrong got happened in the moving process, as I am running this script on the Hadoop Cluster, so it might be possible that cluster went down while this was running etc etc. So how can I have better error handling mechanism in this shell script? Any thoughts?

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  • What is the Effect of Declaring 'extern "C"' in the Header to a C++ Shared Library?

    - by Adam
    Based on this question I understand the purpose of the construct in linking C libraries with C++ code. Now suppose the following: I have a '.so' shared library compiled with a C++ compiler. The header has a 'typedef stuct' and a number of function declarations. If the header includes the extern "C" declaration... #ifdef __cplusplus extern "C" { #endif // typedef struct ...; // function decls #ifdef __cplusplus } #endif ... what is the effect? Specifically I'm wondering if there are any detrimental side effects of that declaration since the shared library is compiled as C++, not C. Is there any reason to have the extern "C" declaration in this case?

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  • OSError: [Error 1] Operation not permitted

    - by user1357576
    I am trying to run a python script which uses a binary file (xFiles.bin.addr_patched) created by a postlinker. However, I am getting this error. File "abc.py", line 74, in ParseCmd shutil.copy(gOptions.inputX, gWorkingXFile) File "/usr/lib/python2.6/shutil.py", line 89, in copy copymode(src, dst) File "/usr/lib/python2.6/shutil.py", line 66, in copymode os.chmod(dst, mode) OSError: [Errno 1] Operation not permitted: 'myPath/xFiles.bin.addr_patched' When I checked the permissions of this xFiles.bin, by ls-l, it shows that -rwxrwxrwx 1 nobody nogroup I presume the error is because this file was created by some other application, the python script I am running does not have access to it. Since I am beginner wrt ubuntu, I don't really know how to fix it. Any suggestions on how to fix this? SOLVED: As one of the answers Suggested : chown username:groupname file name fixes this issue

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  • C++ class functions calling fortran subroutine

    - by user2863626
    Okay so I am trying to make my code work. It is a simple C++ program with a class "CArray". This class has 2 properties, the array size, and the value. I want the main C++ program to create two instances of the class CArray. In the class CArray, I have a function called "AddArray( CArray )" where it adds another array to the current array. The problem I am stuck with, is that I want the function "AddArray" to add the two arrays in fortran. I know, much more complicated, but that is what I need. I am having issues with linking the two inside the class code. #include <iostream> using namespace std; class CArray { public: CArray(); ~CArray(); int Size; int* Val; void SetSize( int ); void SetValues(); void GetArray(); extern "C" { void Add( int*, int*, int*, int*); void Subtract( int*, int*, int*, int*); void Muliply( int*, int*, int *, int* ); } void AddArray( CArray ); void SubtractArray( CArray ); void MultiplyArray( CArray ); }; Also here is the CArray function file. #include "Array.h" #include <iostream> using namespace std; CArray::CArray() { } CArray::~CArray() { } void CArray::SetSize( int s ) { Size = s; for ( int i=0; i<s; i++ ) { Val = new int[Size]; } } void CArray::SetValues() { for ( int i=0; i<Size; i++ ) { cout << "Element " << i+1 << ": "; cin >> Val[i]; } } void CArray::GetArray() { for ( int i=0; i<Size; i++ ) { cout << Val[i] << " "; } } void CArray::AddArray( CArray a ) { if ( Size == a.Size ) { Add(&Val, &a.Val); } else { cout << "Array dimensions do not agree!" << endl; } } void CArray::SubtractArray( CArray a ) { Subtract( &Val, &a, &Size, &a.Size); GetArray(); } Here is my Fortran code. module SubtractArrays use ico_c_binding implicit none contains subroutine Subtract(a,b,s1,s2) bind(c,name='Subtract') integer s1,s2 integer a(s1),b(s2) if ( s1.eq.s2 ) do i=1,s1 a(i) = a(i) - b(i) end return end end If someone could just help me with setting me up to send arrays of integers from C++ classes to fortran I would greatly appreciate it! Thank you, Josh Derrick

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  • Bash command that prints a message on stderr

    - by Salman A
    I want to know if there is a built-in BASH command that prints some text on stderr, just like the echo command that prints text on stdout. I don't want to use temporary io-redirection. I use a built-in command to generate an error on stderr such as ls --asdf (ls: unrecognized option '--asdf') but I want something neater,

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  • Why does my Perl TCP server script hang with many TCP connections?

    - by viraptor
    I've got a strange issue with a server accepting TCP connections. Even though there are normally some processes waiting, at some volume of connections it hangs. Long version: The server is written in Perl and binds a $srv socket with the reuse flag and listen == 5. Afterwards, it forks into 10 processes with a loop of $clt=$srv->accept(); do_processing($clt); $clt->shutdown(2); The client written in C is also very simple - it sends some lines, then receives all lines available and does a shutdown(sockfd, 2); There's nothing async going on and at the end both send and receive queues are empty (as reported by netstat). Connections last only ~20ms. All clients behave the same way, are the same implementation, etc. Now let's say I'm accepting X connections from client 1 and another X from client 2. Processes still report that they're idle all the time. If I add another X connections from client 3, suddenly the server processes start hanging just after accepting. The first blocking thing they do after accept(); is while (<$clt>) ... - but they don't get any data (on the first try already). Suddenly all 10 processes are in this state and do not stop waiting. On strace, the server processes seem to hang on read(), which makes sense. There are loads of connections in TIME_WAIT state belonging to that server (~100 when the problem starts to manifest), but this might be a red herring. What could be happening here?

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