Skip to main content

Seamless Error Highlighting

A lot of output can be generated when you compiling large projects. When it breaks, it can be difficult to identify the particular spot in the build-process where things when wrong. Highlighting the error messages can help them stand out from the rest of the output.

ANSI escape sequences can be used to modify how your terminal window displays its text. For example, outputting the sequence \033[41;37mHello World\033[0m would result in "Hello World" displayed in white text against a red background. Escape sequences begin with an escape character (ASCII 27, octal 033) and bracket. The control values are then given (multiple values are semicolon-separated) and the entire sequence closes with m.

You can highlight certain messages by routing the STDOUT and STDERR streams to sed and performing a replacement.
s,(.*error.*|.*fail.*|.*undef.*),\033[41;37m\1\033[0m,gi
The values you match are of course entirely up to your discretion.

The tricky part is quoting and escaping the expression correctly so various meta-characters aren't intercepted by the shell. And some implementations of sed won't correctly convert \033 to an escape character, so you may need to enter it directly by typing CTRL+V, CTRL+[. Depending on your terminal, an actual escape character may be displayed as ^[ or a special glyph like ESC when you enter it.
make install 2>&1 | sed -e \
's,\(.*error.*\|.*fail.*\|.*undef.*\),ESC[41;37m\1ESC[0m,gi'
If you find yourself using such highlighting often, you may want to define a function to save yourself some typing. For example, with bash you can add something like this to your .bashrc file:
function make() {
/usr/bin/make $@ 2>&1 | sed -e \
's,\(.*error.*\|.*fail.*\|.*undef.*\),ESC[41;37m\1ESC[0m,gi';
}
You can type make install at the prompt like you normally would. bash will call the new make() function, which in turn calls the actual make utility with any arguments (such as install) and colorizes the output. Error highlighting is now seamless and automatic!
Labels:

Comments

Post a Comment

Popular posts from this blog

Writing a Minimal PSR-0 Autoloader

An excellent overview of autoloading in PHP and the PSR-0 standard was written by Hari K T over at PHPMaster.com , and it's definitely worth the read. But maybe you don't like some of the bloated, heavier autoloader offerings provided by various PHP frameworks, or maybe you just like to roll your own solutions. Is it possible to roll your own minimal loader and still be compliant? First, let's look at what PSR-0 mandates, taken directly from the standards document on GitHub : A fully-qualified namespace and class must have the following structure \<Vendor Name>\(<Namespace>\)*<Class Name> Each namespace must have a top-level namespace ("Vendor Name"). Each namespace can have as many sub-namespaces as it wishes. Each namespace separator is converted to a DIRECTORY_SEPARATOR when loading from the file system. Each "_" character in the CLASS NAME is converted to a DIRECTORY_SEPARATOR . The "_" character has no special ...
6 comments
Read more

Safely Identify Dependencies for Chrooting

The most difficult part of setting up a chroot environment is identifying dependencies for the programs you want to copy to the jail. For example, to make cp available, not only do you need to copy its binary from /bin and any shared libraries it depends on, but the dependencies can have their own dependencies too that need to be copied. The internet suggests using ldd to list a binary’s dependencies, but that has its own problems. The man page for ldd warns not to use the script for untrusted programs because it works by setting a special environment variable and then executes the program. What’s a security-conscious systems administrator to do? The ldd man page recommends objdump as a safe alternative. objdump outputs information about an object file, including what shared libraries it links against. It doesn’t identify the dependencies’ dependencies, but it’s still a good start because it doesn’t try to execute the target file. We can overcome the dependencies of depende...
Post a Comment
Read more

A Unicode fgetc() in PHP

In preparation for a presentation I’m giving at this month’s Syracuse PHP Users Group meeting, I found the need to read in Unicode characters in PHP one at a time. Unicode is still second-class in PHP; PHP6 failed and we have to fallback to extensions like the mbstring extension and/or libraries like Portable UTF-8 . And even with those, I didn’t see a unicode-capable fgetc() so I wrote my own. Years ago, I wrote a post describing how to read Unicode characters in C , so the logic was already familiar. As a refresher, UTF-8 is a multi-byte encoding scheme capable of representing over 2 million characters using 4 bytes or less. The first 128 characters are encoded the same as 7-bit ASCII with 0 as the most-significant bit. The other characters are encoded using multiple bytes, each byte with 1 as the most-significant bit. The bit pattern in the first byte of a multi-byte sequence tells us how many bytes are needed to represent the character. Here’s what the function looks like: f...
1 comment
Read more