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Tag: linux

Windows Executable file structure

I know that generally the object file has code, data, heap and stack sections. But I want to know how this is arranged in windows executables and Linux executables. I searched on internet and found some structure. I understood .text is for code and .data is for global variables. I want to know here is the sta…

Is rename() atomic?

I am not being able to check this via experiments and could not gather it from the man pages as well. Say I have two processes, one moving(rename) file1 from directory1 to directory2. Say the other process running concurrently copies the contents of directory1 and directory2 to another location. Is it possibl…

Bash/sh ‘if else’ statement

I want to understand the if else statement in sh scripting. So I wrote the below to find out whether JAVA_HOME is set in the environment or not. I wrote the below script This my output to env: But I get the below output: Answer You’re running into a stupid limitation of the way sh expands arguments. Lin…

Compiling C Program on OS X to Run on Linux

I have a pretty simple C program that does some cryptographic calculations using only standard library functions. I will be running the program on Ubuntu (10.04, 32 bit) and compiled it on OS X 10.6 using cc with the -m32 flag. When I tried to run it on Ubuntu I got the error message “cannot execute bin…

What does the brk() system call do?

According to Linux programmers manual: brk() and sbrk() change the location of the program break, which defines the end of the process’s data segment. What does the data segment mean over here? Is it just the data segment or data, BSS, and heap combined? According to wiki Data segment: Sometimes the dat…

xterm keep page from less in terminal after exit

I often view files using less and want to remember what i have just seen in the file. However when I quit less by pressing the q key my xterm window removes the page of less showing the file and only shows my command prompt. How do I keep the less output on my terminal when I quit? Answer less

linux shell title case

I am wrinting a shell script and have a variable like this: something-that-is-hyphenated. I need to use it in various points in the script as: something-that-is-hyphenated, somethingthatishyphenated, SomethingThatIsHyphenated I have managed to change it to somethingthatishyphenated by stripping out – us…