Coding School

Problem
You want to get up and running with sqlite

Solution
Install sqlite3 on linux, via yum: yum install sqlite3Then just run sqlite dbname

Example
% sqlite3 testdata.dbSQLite version 3.5.9Enter “.help” for instructionssqlite> create table memos(text,priority INTEGER);sqlite> insert into memos values(’deliver project description’,10);sqlite> insert into memos values(’lunch with Christine’,100);sqlite> select * from memos;deliver project description|10lunch with Christine|100sqlite>

Reference
sqlite3 linux man [...]

Problem
Getting an error about not being able to find libraries (file not found), when starting up a binary – such as httpd.

Solution
You need to identify the shared libraries required by your binary. Ordinarly we use the ldd command for this and amended LD_LIBRARY_PATH to find the libs – see example below.You might also want to [...]

Problem
Different versions of UNIX handle the stripping of newlines in a string differently. Obviously if you echo a string, the shell automatically expands newlines “\n”.

Solution
sed and tr don’t appear to like performing these substitutions. But with Perl its a steal.

Example
% echo ‘hello world\nhello world\ntest it’ | perl -ane ’s#\\n# #g; print,”";’hello world hello [...]

Problem
You want to resize images from the command line.

Solution
Use image magik mogrify command.mogrify -resize “percentage” image_naAlso you can view current sizing – like this:% identify IMG_3864.JPGIMG_3864.JPG JPEG 563×422 563×422+0+0 DirectClass 8-bit 32.8887kb

Example
mogrify -resize 20% IMG_3705.JPG

Reference
Technorati Tags: mogrifymogrify man page – resize an image

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Problem
You want to listen on a pipe and perform commands, based on the text sent to the pipe.This could be useful for triggering action based on events;Running code as different users – i.e. allow root or a functional user to run something – just need to allow access to group of users, via permission to [...]

Problem
You want to get notified when a file arrives. Maybe it is coming in from somewhere else, or just is the result of some processing.What ever the case, never sit there waiting for a file to arrive again!

Solution
Put the code under example tab, in a cron entry. See reference for more detail [...]

Problem
You want to debug a running process on Solaris?You want to debug running process on Linux?

Solution
See the example for debugging processes on Solaris or Linux – the syntax shows all system executes and reads.

Example
truss -xall -vall -rall -t’read’ -p PID #To run a command and have it produce [...]

Problem
You want to trace program execution on Solaris?You want to perform network tracing on Solaris?Perform a text dump of a binary file – or see ascii codes, etc?Generate some random data?List directory contents in 3 columns?Loop through a list of files and perform actions on them?Check for values in vars?Detach a process without it dying.Perform [...]

Problem
You want to find a pattern in a file and have the line displayed.

Solution
I “discovered” this undocument (well in all the doco I’ve ever read), pretty much by accident.Basically find produces a list of files (type f), in the current directory and supplies them individually to the grep command. Ordinarily if grep is supplied [...]

Problem
Ever need to look at a file, but have not been able to – due to hidden control characters, etc.

Solution
Or just needed to see spaces and end of line characters, comparing files, etc. Optical dump or more specifically the od command, can be extremely useful for display ascii characters. See the example.

Example
The basic syntax [...]