If you want to change the modification time of a file on Linux, the command you’re looking for is touch. You can use touch with the -r parameter to specify a reference file who’s date and time information will be used as the basis for a new (or existing) file.
It took me a while, but I finally figured out how to print a number from a bash script properly formatted with commas as thousand’s separators. For those like me who weren’t in the know, the magical incantation is:
printf "%'d" 123456
That will format 123456 as 123,456. Much easier to read when you’re dealing with large numbers such as the sizes of files in gigabytes.
So now if I could only find the Unix command that took a number of bytes and turned it into an approximate value with GB or MB suffixes.
I’ve been restoring my archives — 10,000,000 files from the past 13 years — and while I did so I had a little bit of a trip down memory lane. I found some old Visual Basic 6 database programs that I wrote when I was in high school, including a phone book, a diary, a time sheeting system, and a few other miscellaneous tools. In order to get them to run I had to get my compiler out to fix a few data object dependencies (DAO5) and a few hardcoded configuration settings such as the paths to database files. So I reinstalled my old VB6 development environment, which I’m pleased to say still works (although I’m still running Windows XP). Good fun. :)
I have a directory structure with archived files, many of which are zipped or tarballed up. So if I want to search for a file, I can’t really be sure that the file I’m looking for isn’t in a compressed file. So I wrote some scripts to automatically run over a directory tree and automatically extract any compressed files that it finds there. There are a few extra features, such as if the file is larger than 10MB then it will prompt for whether to extract it or not. I have a few other features for handling errors to add in, but I’m happy to post this version up now.
#!/bin/bash
err=$1
err=${err:-1}
search() {
find -iname "*$1" -print0 | xargs -i -0 `dirname "$0"`/extract-file.sh "$1" "$2" "$err" "{}"
}
search ".tar.gz" "tar xf"
search ".tgz" "tar xf"
search ".zip" "unzip -q"
#!/bin/bash exec 0< /dev/tty path="$4" file_name=`basename "$path"` dir_name=`dirname "$path"` new_name=`basename "$path" "$1"` new_path="$dir_name/$new_name" [ -e "$new_path" ] && exit 0 echo $dir_name/$file_name file_size=`stat -c %s "$path"` #echo -n "File is $file_size bytes." printf "File is %'d bytes." $file_size check=`echo "$file_size < 10485760" | bc` if [ "$check" = "1" ]; then answer="y"; fi while [ "$answer" != "y" ]; do read -n 1 -s -p " Extract? " answer [ "$answer" = "n" ] && echo && echo && exit 0 done echo mkdir "$new_path" pushd "$new_path" > /dev/null 2>&1 $2 "../$file_name" if [ "$?" != "0" ]; then popd > /dev/null 2>&1 rm -rf "$new_path" echo answer="" while [ "$answer" != "y" ]; do read -n 1 -s -p "Do you want to ignore this file? " answer [ "$answer" = "n" ] && exit $3 done fi popd > /dev/null 2>&1 echo
It took me a while, but I finally found this documentation which said that you use the single quote to flag formatted output as having the thousands separator when using printf.
MD5 in C++ is everywhere if you search for it (except for in the standard library or in boost, which isn’t what I would have expected), but I only needed one implementation and I found this one: RSA Data Security, Inc. MD5 Message-Digest Algorithm.
I wanted to figure out how to tell if my code was compiling in Visual Studio or somewhere else (GCC probably), and I found that you can use #ifdef _MSC_VER.
I was having a problem where Visual Studio was saying that “windows.h” could not be found after having installed the Windows SDK v7.1. I found this article which said to update the path in “HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SDKs\Windows\CurrentInstallFolder” in the registry. So I did that, and now everything is working.
I did my first operator overloading in C++ today. My code ended up being quite different to the example code that I found, but I think I’m happy with it:
class FileData {
public:
FileData( const string& path );
static bool LessThan( const FileData& a, const FileData& b );
bool operator< ( const FileData& );
unsigned long size() const { return m_size; }
private:
unsigned long m_size;
char m_md5[ 16 ];
};
static bool operator< ( const FileData& a, const FileData& b ) {
return FileData::LessThan( a, b );
}
bool FileData::operator< ( const FileData& b ) {
return FileData::LessThan( *this, b );
}
bool FileData::LessThan ( const FileData& a, const FileData& b ) {
unsigned long a_size = a.size();
unsigned long b_size = b.size();
if ( a_size == b_size ) {
return memcmp( a.m_md5, b.m_md5, 16 ) < 0;
}
return a_size < b_size;
}
I'm not sure when it becomes either useful or necessary to define the operator both as a static and as a member function. I did both because I wasn't sure what was required.
I was curious about the difference between C++ pointers and C++ references, so I searched and found this which says that basically: