UNIX for Beginners Questions & Answers

The od output clearly shows us that test.sh is not a shell script. Shell scripts are UNIX text files. UNIX text files have a single <newline> character as a line terminator on every line (not the DOS <carriage-return><newline> character pairs as line separators with no line terminator at the end of the file). The <carriage-return> characters in test.sh are extraneous characters at the end of all but the last line in your shell script. They are interpreted as part of the last string on each command line (i.e., as part of a filename operand, as the unknown string then<carriage-return> when the shell keyword then was expected, etc.) and are causing you lots of problems that are sometimes hard to diagnose because the diagnostic messages print the <carriage-return> characters but they frequently are invisible on the screen after they have been printed.

In the shell command language there are single-quotes ('), double-quotes ("), and back-quotes (`). Opening and closing double-quotes (“″) and opening and closing single-quotes (‘') may look nice in pretty-printed text, but they are syntax errors in a shell script.

Yes, you can use ls -t | head -n1 in a shell script and compare the results to the string saved in the variable FILENAME_WANTED by the command:

Code:

FILENAME_WANTED=`date +"HourlyDate_%Y%m%d_%H00.txt"`

but, if instead of the above command you use the command:

Code:

FILENAME_WANTED=`date +"HourlyDate_%Y%m%d_%H00.txt"`<CR>

where <CR> is a visual representation of the <carriage-return> character you have in your current version of test.sh, there will never be a match because the string saved in FILENAME_WANTED contains a trailing <carriage-return> character that is not present in the filename you are reading from ls.

If you want to use notepad instead of learning how to use vi, you must configure it to use UNIX line terminators; not DOS line separators and you must configure it to use shell command language single-quotes (not pretty-printed opening an closing single-quotes), double-quotes (not pretty-printed opening and closing double-quotes), and back-quotes (instead of pretty printed single-quotes) or learn to use the highly preferred $(command) form of command substitution instead of the obsolete `command` form of command substitution and stop using back-quotes in your shell scripts.

Hello Don,

I finally used vi editor and got it working ..

Code:

# Vani Sonti
# 07/14/2016
# find file name match and load data only when a match found 
# if not display msg
#!/usr/bin/sh
FILENAME_WANTED=`date +"HourlyData_%Y%m%d_%H00.txt"`
echo "FILENAME_WANTED = $FILENAME_WANTED"
LIST_OF_FILES=`ls -rt /tmp/v_tst/HourlyData*.txt |tail -1`
echo "LIST_OF_FILES = $LIST_OF_FILES"
echo "------"
if [ "$FILENAME_WANTED" = "$LIST_OF_FILES" ]; then 
echo "matched"
else echo "NotMatched"
fi

output looks this:

Code:

perseus.gasleak(/tmp/v_tst)% sh chk.sh
FILENAME_WANTED = HourlyData_20160714_1200.txt
LIST_OF_FILES = /tmp/v_tst/HourlyData_20160714_1000.txt
------
NotMatched
perseus.gasleak(/tmp/v_tst)%

Everyone, appreciate all your help

Vani