What are the differences between poll and select?
I am referring to the POSIX standard select and poll system C API calls. 3 Answers 3
unix
Print a file’s last modified date in Bash
I can’t seem to find how to print out the date of a file. I’m so far able to print out all the files in a directory, but I need to print out the dates with it. I know I need to attach a date format with the echo of the entry, but all I … Read more
How to kill a child process after a given timeout in Bash?
I have a bash script that launches a child process that crashes (actually, hangs) from time to time and with no apparent reason (closed source, so there isn’t much I can do about it). As a result, I would like to be able to launch this process for a given amount of time, and kill … Read more
How do you run a single query through mysql from the command line?
I’m looking to be able to run a single query on a remote server in a scripted task. For example, intuitively, I would imagine it would go something like: mysql -uroot -p -hslavedb.mydomain.com mydb_production “select * from users;” 7 Answers 7
Setting PATH environment variable in OSX permanently
I have read several answers on how to set environmental variables on OSX as permanently. First, I tried this, How to permanently set $PATH on Linux/Unix? but I had an error message saying no such file and directory, so I thought I could try ~/.bash_profile instead of ~/.profile but it did not work. Second, I … Read more
What is the reason for performing a double fork when creating a daemon?
I’m trying to create a daemon in python. I’ve found the following question, which has some good resources in it which I am currently following, but I’m curious as to why a double fork is necessary. I’ve scratched around google and found plenty of resources declaring that one is necessary, but not why. Some mention … Read more
How can I convert a file pointer ( FILE* fp ) to a file descriptor (int fd)?
I have a FILE *, returned by a call to fopen(). I need to get a file descriptor from it, to make calls like fsync(fd) on it. What’s the function to get a file descriptor from a file pointer? 3 Answers 3
How to get the current directory in a C program?
I’m making a C program where I need to get the directory that the program is started from. This program is written for UNIX computers. I’ve been looking at opendir() and telldir(), but telldir() returns a off_t (long int), so it really doesn’t help me. How can I get the current path in a string … Read more
Get the date (a day before current time) in Bash
How can I print the date which is a day before current time in Bash? 17 Answers 17
Sorting a tab delimited file
I have a data with the following format: foo<tab>1.00<space>1.33<space>2.00<tab>3 Now I tried to sort the file based on the last field decreasingly. I tried the following commands but it wasn’t sorted as we expected. $ sort -k3nr file.txt # apparently this sort by space as delimiter $ sort -t”\t” -k3nr file.txt sort: multi-character tab `\\t’ … Read more
