Pipe input into a script

Question

I have written a shell script in ksh to convert a CSV file into Spreadsheet XML file. It takes an existing CSV file (the path to which is a variable in the script), and then creates a new output file .xls. The script has no positional parameters. The file name of the CSV is currently hardcoded into the script.

I would like to amend the script so it can take the input CSV data from a pipe, and so that the .xls output data can also be piped or redirected (>) to a file on the command line.

How is this achieved?

I am struggling to find documentation on how to write a shell script to take input from a pipe. It appears that 'read' is only used for std input from kb.

Thanks.

Edit : script below for info (now amended to take input from a pipe via the cat, as per the answer to the question.

#!/bin/ksh #Script to convert a .csv data to "Spreadsheet ML" XML format - the XML scheme for Excel 2003 # #   Take CSV data as standard input #   Out XLS data as standard output #  DATE=`date +%Y%m%d`  #define tmp files INPUT=tmp.csv IN_FILE=in_file.csv  #take standard input and save as $INPUT (tmp.csv) cat > $INPUT  #clean input data and save as $IN_FILE (in_file.csv) grep '.' $INPUT | sed 's/ *,/,/g' | sed 's/, */,/g' > $IN_FILE  #delete original $INPUT file (tmp.csv) rm $INPUT  #detect the number of columns and rows in the input file ROWS=`wc -l < $IN_FILE | sed 's/ //g' ` COLS=`awk -F',' '{print NF; exit}' $IN_FILE` #echo "Total columns is $COLS" #echo "Total rows  is $ROWS"  #create start of Excel File echo "<?xml version=\"1.0\"?> <?mso-application progid=\"Excel.Sheet\"?>  <Workbook xmlns=\"urn:schemas-microsoft-com:office:spreadsheet\"         xmlns:o=\"urn:schemas-microsoft-com:office:office\"         xmlns:x=\"urn:schemas-microsoft-com:office:excel\"         xmlns:ss=\"urn:schemas-microsoft-com:office:spreadsheet\"         xmlns:html=\"http://www.w3.org/TR/REC-html40\"> <DocumentProperties xmlns=\"urn:schemas-microsoft-com:office:office\">       <Author>Ben Hamilton</Author>       <LastAuthor>Ben Hamilton</LastAuthor>       <Created>${DATE}</Created>       <Company>MCC</Company>       <Version>10.2625</Version> </DocumentProperties> <ExcelWorkbook xmlns=\"urn:schemas-microsoft-com:office:excel\">         <WindowHeight>6135</WindowHeight>         <WindowWidth>8445</WindowWidth>         <WindowTopX>240</WindowTopX>         <WindowTopY>120</WindowTopY>         <ProtectStructure>False</ProtectStructure>         <ProtectWindows>False</ProtectWindows> </ExcelWorkbook>  <Styles>       <Style ss:ID=\"Default\" ss:Name=\"Normal\">             <Alignment ss:Vertical=\"Bottom\" />             <Borders />             <Font />             <Interior />             <NumberFormat />             <Protection />       </Style>       <Style ss:ID=\"AcadDate\">       <NumberFormat ss:Format=\"Short Date\"/>           </Style>  </Styles> <Worksheet ss:Name=\"Sheet 1\"> <Table> <Column ss:AutoFitWidth=\"1\" />"  #for each row in turn, create the XML elements for row/column r=1 while (( r <= $ROWS )) do    echo "<Row>\n"      c=1     while (( c <= $COLS ))     do         DATA=`sed -n "${r}p" $IN_FILE | cut -d "," -f $c `          if [[ "${DATA}" == [0-9][0-9]\.[0-9][0-9]\.[0-9][0-9][0-9][0-9] ]]; then              DD=`echo $DATA | cut -d "." -f 1`             MM=`echo $DATA | cut -d "." -f 2`             YYYY=`echo $DATA | cut -d "." -f 3`                  echo "<Cell ss:StyleID=\"AcadDate\"><Data ss:Type=\"DateTime\">${YYYY}-${MM}-${DD}T00:00:00.000</Data></Cell>"         else                     echo "<Cell><Data ss:Type=\"String\">${DATA}</Data></Cell>"          fi         (( c+=1 ))     done     echo "</Row>"    (( r+=1 )) done  echo "</Table>\n</Worksheet>\n</Workbook>"   rm $IN_FILE > /dev/null  exit 0 

Answer 1

Commands inherit their standard input from the process that starts them. In your case, your script provides its standard input for each command that it runs. A simple example script:

#!/bin/bash cat > foo.txt 

Piping data into your shell script causes cat to read that data, since cat inherits its standard input from your script.

$ echo "Hello world" | myscript.sh $ cat foo.txt Hello world 

The read command is provided by the shell for reading text from standard input into a shell variable if you don't have another command to read or process your script's standard input.

#!/bin/bash  read foo echo "You entered '$foo'"  $ echo bob | myscript.sh You entered 'bob'