seq.sh - embeded seq
Kind of embedded seq. Sometimes happens that you need a bunch of text lines with some periodically changing numeric values in them. Usually for download with wget.
But sadly, with all it’s almost omnipotent parameters, using wget can be difficult if there is no index page with followable links or the thumbnails are messed between
the full size pictures. So you will have to do more single-file downloads instead of one recursive. And you will use the -i switch and an input file. But how you can
create that file easier ? Naturally, with a for and a seq :
Bash code - old, deprecated example
for i in `seq 10`; do wget http://example.com/public/file_$i.txt; done
Note
In meantime Bash’s brace expansion was significantly improved :
- Bash 2.05 introduced brace expansion for series of values
{a,b,c,d,e,f} - Bash 3.0 introduced sequence expansion for numbers
{1..10}and letters{a..z} - Bash 4.0 introduced sequence increment
{1..10..2}and zero padding{01..10}
Bash code - new, modern example
wget http://www.example.com/public/file_{1..10}.txt
Usage
seq.sh makes this easier. You just mark the expandable values and seq.sh will generate the list of strings. The marks are of form :
{[-w] [from [by]] to}- the usual parameters for seq command{#level}- replace with the value of the given counter
For more details see the man page.
So this file :
sample input
http://www.example.net/archive/{2003 2004}-{-w 3 3 12}.zip
http://www.example.com/gallery{2}/pamela_a_{#1}/{3}_{#2}.jpg
will be transformed into this :
sample output - seq.sh < input.txt
http://www.example.net/archive/2003-03.zip http://www.example.net/archive/2003-06.zip http://www.example.net/archive/2003-09.zip http://www.example.net/archive/2003-12.zip http://www.example.net/archive/2004-03.zip http://www.example.net/archive/2004-06.zip http://www.example.net/archive/2004-09.zip http://www.example.net/archive/2004-12.zip http://www.example.com/gallery1/pamela_a_1/1_1.jpg http://www.example.com/gallery1/pamela_a_1/2_2.jpg http://www.example.com/gallery1/pamela_a_1/3_3.jpg http://www.example.com/gallery2/pamela_a_2/1_1.jpg http://www.example.com/gallery2/pamela_a_2/2_2.jpg http://www.example.com/gallery2/pamela_a_2/3_3.jpg
Configuration
None.
Not even command line parameters exist.
Versions
- 1.0
- Initial release.
- 1.1 - December 2004
- Placeholders prefixed with hash ( # ) are replaced with the sequential value of the placeholder with the given order number.
- 1.2 - April 2008
- Minor optimizations.
- Portable sh code replaced with Bash specific alternatives.
Plans
- Should be nice to make it to use character sequences and roman numbers. ( Ok, the second is just a joke. )
- As far as is used for URLs, the
{..}markup is ok, but it should be setable through parameters.
Download
You can find the related files on GitHub in my Bash-script repository’s seq directory :
- seq.sh - script
- seq.sh.1 - man page
- seq.sh.pod - man page source