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--- tutorials:bash_scripting:part1 [2012/02/26 05:52] – rmiles
+++ tutorials:bash_scripting:part1 [2017/10/12 21:58] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
-**1. Converting a scanned document to a pdf document**
+//**1. Converting a scanned document to a pdf document**//
+----
 Last year I did some consulting for a law firm that required me to submit time sheets with my invoices. In any given invoice period I would undertake work involving multiple clients. Work undertaken for each client was broken down into standard categories, telephone call, email, meeting, etc.
@@ Line 41: / Line 42: @@
 I will now explain how this script works:
-Note that with the exception of the first line, any text prefixed with a hash, //#//, is ignored up until the next new line. Text prefixed with a hash is usually referred to as a comment. Comments can be put on the same line as a command but only after the command. There are no hard and fast rules about using comments. They are handy to explain things to other folks as well as oneself. I normally don't comment a small script as much as this one. Usually I just add some notes at the top and then add what I need as I go along to explain what's happening or why something needs to done a certain way
+Note that with the exception of the first line, any text prefixed with a hash, //#//, is ignored up until the next new line. Text prefixed with a hash is usually referred to as a comment. Comments can be put on the same line as a command but only after the command. There are no hard and fast rules about using comments. They are handy to explain things to other folks as well as oneself. I normally don't comment a small script as much as this one. Usually I just add some notes at the top and then perhaps add commets to explain why something is done a certain way for future reference.
 <code bash>
 #!/bin/bash
@@ Line 59: / Line 59: @@
 </code>
-This line uses //test// a bash built in command (builtin) to test if the variable is a non zero string, i.e. if a file name was passed to the script when the command //contopdf// was run. //Test// will exit with an exit status of 0 (true) if //input_file// is a non zero string and 1 (false) if //input_file// is not a non zero string. The exit does not print to stdout but it can be assigned as a variable using //$?// and can then be evaluated using an //if statement//.
+This line uses //test// a bash built in command (builtin) to test if the variable is a non zero string, i.e. if a file name was passed to the script when the command //contopdf// was run. //Test// will exit with an exit status of 0 (true) if //input_file// is a non zero string and 1 (false) if //input_file// is not a non zero string. The exit code does not print to stdout but it can be assigned as the variable //$?// and can then be evaluated using an //if statement//.
 <code bash>
@@ Line 81: / Line 81: @@
 </code>
-Instead of passing both an input filename and an output (save) filename to the script the next line to creates and assigns an output filename to the variable //output_file//. Variables can be assigned using the output of a command when the command is enclosed in two backticks, //`//, which is the symbol below the tlde.
+Instead of passing both an input filename and an output (save) filename to the script the next line to assign an output filename to the variable //output_file//. Variables can be assigned using the output of a command when the command is enclosed in two backticks, //`[command`//.
-In the command echo is used to print the variable //input_file// but instead of printing to stdout it is redirected with a pipe to //awk//.
+In this line echo is used to print the variable //input_file// but instead of printing to stdout it is redirected with a pipe to //awk//.
-//Awk// or //gawk// is a pattern matching program. Here the flag //-F// is used to declare //"."// (full stop) as the field separator. For example, the file name //scanned_image.png// consists of two fields separated by a full stop. Awk will print the first field, //$1// (scanned_file) to stdout.
+//Awk//, or //gawk//, is a pattern matching program. Here the flag //-F// is used to declare //"."// (full stop) as the field separator. For example, the file name //scanned_image.png// consists of two fields separated by a full stop. Awk will print the first field, //$1// (scanned_file) to stdout.
+Note //.pdf// on the same line, after the second backtick. This appends //.pdf// to //$1// so if //$1// was scanned_file, the variable //output_file// would be scanned_file.pdf.
+You will find that there are often more than one way to do something when scripting. The command //cut// could also have been used in place of awk.
+<code bash>
+output_file=`echo "$input_file" | cut -d. -f1`.pdf
+</code>
-Note //.pdf// on the same line, after the second backtick. This appends //.pdf// to //$1// so if //$1// was scanned_file, the variable //output_file// would be scanned_file.pdf
+Field separators are also referred to as delimiters. In the above line, //-d.// nominates full stop as the delimiter and //-f1// selects field 1 for printing to stdout.
 <code bash>
@@ Line 102: / Line 110: @@
 ----
-I almost always have a terminal open so my scripts are usually intended to be run on the command line. After saving the scanned image into the directory where the relevant pdf records were kept I would //cd// into that directory and run the command //con2pdf [image name]//.
+//I almost always have a terminal open so my scripts are usually intended to be run on the command line. After saving the scanned image into the directory where the relevant pdf records were kept I would //cd// into that directory and run the command //con2pdf [image name]//.
-In the next section I'll show how to modify //con2pdf// so that it will have a gui interface for both selecting the image file and selecting a path and name for the resulting .pdf file
+In the next section I'll show how to modify //con2pdf// so that it will have a gui interface for both selecting the image file and selecting a path and name for the resulting .pdf file//
 ----
+**Cheers!**