Author: rchapin

Removing the Last Token From a String in Bash with awk

Posted on by rchapin

Let’s say that you have some number of files for which you want to create a containing directory that is named with all but the last token of the file name, and you want to remove just the last token to create the name of the directory.

Much easier to explain with an example.  Given this list of files:

ls -1
foo_10_10_sometrash
foo_1_sometrash
foo_2_sometrash
foo_3_sometrash
foo_4_sometrash
foo_5_5_sometrash
foo_5_sometrash
foo_6_6_sometrash
foo_7_7_sometrash
foo_8_8_sometrash
foo_9_9_sometrash

You want to create a directory for each → Continue reading “Removing the Last Token From a String in Bash with awk”

Backspace, Delete, and/or Return Key Stops Working in Oracle SQL Developer

Posted on by rchapin

So, I fire up SQL Developer to run some queries against a QC server and for some reason, I am no longer able to use the backspace, delete, or return keys to edit .sql files opened in the program.

I tried opening a new .sql file, and restarting SQL Developer.  I then tried restarting Windows.  None of those worked.

After a bit of searching I found a forum posting that indicated by going to Tools/Preferences/Accelerators and clicking the “Load Preset…” → Continue reading “Backspace, Delete, and/or Return Key Stops Working in Oracle SQL Developer”

Checking that Input or a Variable is an Integer in BASH

Posted on by rchapin

Here is a quick snippet for checking whether or not a variable is a valid integer in BASH.  It is also a howto for regular expressions in a shell script.

# Make sure that FOO is an integer
if [[ ! "$FOO" =~ ^[0-9]+$ ]]; then
        echo "The FOO was NOT an integer"
fi
→ Continue reading “Checking that Input or a Variable is an Integer in BASH”

How To Benchmark Disk I/O

Posted on by rchapin

Here is a quick snipped on how to benchmark Disk I/O with dd.

time sh -c "dd if=/dev/zero of=/home/rchapin/test.zeros bs=1024k count=10000 && sync"

10000+0 records in
10000+0 records out
10485760000 bytes (10 GB) copied, 81.4124 s, 129 MB/s

real    1m21.950s
user    0m0.810s
sys     0m5.474s

Will do a write test of 10GB.

You can do a similar test and read from that file generated and write to another file or /dev/null to get an idea of the read speeds.

See the → Continue reading “How To Benchmark Disk I/O”

Creating an Array in Bash from a File With Each Element on a Separate Line

Posted on by rchapin

Let’s say that you have a file and you would like to convert each line in the file to an element in an array.

The key to this is knowing about and how to manipulate the IFS (Internal Field Separator).  The default IFS is whitespace (a space, tab, or newline) and if you create an array passing it a whitespace delimited list of strings, each token will be set to an element in the array.

ARRAY=(a b d
→ Continue reading “Creating an Array in Bash from a File With Each Element on a Separate Line”

Installing Chrome Extensions Without Signing in With a Google Account

Posted on by rchapin

Google requires that you login with a Google account before you can install any Chrome extensions.

The following is how to install an extension without logging in (under Windows.  The same should work under Linux and Mac):

  1. Find the ID for the extension.  When you browse the extension in the store you will see a URL similar to the following:  https://chrome.google.com/webstore/detail/cookies/iphcomljdfghbkdcfndaijbokpgddeno?hl=en.   The hash string after the ‘cookies’ string (the name of the extension) up to the ? is the
→ Continue reading “Installing Chrome Extensions Without Signing in With a Google Account”

Removing The Last N Character From a String in Bash Script with sed

Posted on by rchapin

Here is a quick one-liner for trimming a specific number of characters from the end of a string under bash:

# Remove the last 5 characters
$ echo "somestringwith12345" | sed "s/.....$//g"
$ somestringwith

# Remove the last 3 characters
$ echo "somestringwith12345" | sed "s/...$//g"
$ somestringwith12
→ Continue reading “Removing The Last N Character From a String in Bash Script with sed”

Running Multiple Instances of Notepad++ Under Windows 7

Posted on by rchapin

If you want to run multiple versions of Notepad++ under Windows 7 create a .bat file with the following:

"C:\Program Files (x86)\Notepad++\notepad++.exe" -multiInst %1

And simply run the bat file via a cmd prompt/ → Continue reading “Running Multiple Instances of Notepad++ Under Windows 7”

Splitting a String in Bash on the FIRST Occurrence of a Character

Posted on by rchapin

About a year ago I posted an article about how to split into an array of values based on a given delimiter in bash.

The following is how to take that same string and split it on the first occurrence of the same user defined delimiter.

Both use the ‘read’ command, but in a slightly different way.

Instead of passing read the -a [aname] parameter which tells it that “The words are assigned to sequential indices of the array → Continue reading “Splitting a String in Bash on the FIRST Occurrence of a Character”

BASH Script With Default Arguments Defined in The Script

Posted on by rchapin

Often times you will want to write a BASH script where you don’t want to have to keep track of all of the positional command line arguments and/or you might want to configure it with a set of environmental variables while having a default value for each in the script.

Following is the syntax for declaring them in the shell script, and then an example on how to invoke it.

#!/bin/bash

: ${ARG1:="somedefault_arg1"}
: ${ARG2:="10"}

echo "ARG1 = $ARG1"
echo
→ Continue reading “BASH Script With Default Arguments Defined in The Script”
© 2005 Ryan Chapin