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Solved
How to read data from a file to a variable..
Posted on 2004-08-16
Trying to compare the number of files in a directory and make sure that it is increasing over time
I output the result of a ls - l piped to a wc -l
Trying to read in a value (first line) from a file and assign a to a variable... the following is the script.. where am I going wrong ??
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
# Start by copying the old countfile to a new one that will be referenced later
cp /usr/byr/countfile /usr/byr/countfile2
# then pipe the output of the counting of the lines to the countfile
ls -l /usr/byr/ | wc -l > /usr/byr/countfile
# assign the variable $new to the current number of lines
# and assign $old to the previous number of lines
cut -c 1-8 /usr/byr/countfile > $new
cut -c 1-8 /usr/byr/countfile2 > $old
echo $new
echo $old
# then compare the value of the old number to the new number
# and write to the testfile a string that will be looked at by NIGHTWATCH
if [ exp $new -gt exp $old ]; then
echo ok > /usr/byr/testfile
echo $new
echo $old
echo "ok"
elif [ exp $new -eq exp $old ]; then
echo same > /usr/byr/testfile
echo $new
echo $old
echo "same"
else
echo fail > /usr/byr/testfile
echo $new
echo $old
echo "fail"
fi
~
I output the result of a ls - l piped to a wc -l
Trying to read in a value (first line) from a file and assign a to a variable... the following is the script.. where am I going wrong ??
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
# Start by copying the old countfile to a new one that will be referenced later
cp /usr/byr/countfile /usr/byr/countfile2
# then pipe the output of the counting of the lines to the countfile
ls -l /usr/byr/ | wc -l > /usr/byr/countfile
# assign the variable $new to the current number of lines
# and assign $old to the previous number of lines
cut -c 1-8 /usr/byr/countfile > $new
cut -c 1-8 /usr/byr/countfile2 > $old
echo $new
echo $old
# then compare the value of the old number to the new number
# and write to the testfile a string that will be looked at by NIGHTWATCH
if [ exp $new -gt exp $old ]; then
echo ok > /usr/byr/testfile
echo $new
echo $old
echo "ok"
elif [ exp $new -eq exp $old ]; then
echo same > /usr/byr/testfile
echo $new
echo $old
echo "same"
else
echo fail > /usr/byr/testfile
echo $new
echo $old
echo "fail"
fi
~
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27 Comments
Hi 911bob,
Without knowing what your problem is I would improve the script this way:
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
# Start by copying the old countfile to a new one that will be referenced later
mv /usr/byr/countfile /usr/byr/countfile2
# then pipe the output of the counting of the lines to the countfile
ls -l /usr/byr/ | wc -l | read new
echo $new > /usr/byr/countfile
# assign the variable $new to the current number of lines
# and assign $old to the previous number of lines
cat /usr/byr/countfile2 | read old
echo $new
echo $old
# then compare the value of the old number to the new number
# and write to the testfile a string that will be looked at by NIGHTWATCH
if [ $new -gt $old ]; then
echo ok > /usr/byr/testfile
echo $new
echo $old
echo "ok"
elif [ $new -eq $old ]; then
echo same > /usr/byr/testfile
echo $new
echo $old
echo "same"
else
echo fail > /usr/byr/testfile
echo $new
echo $old
echo "fail"
fi
======
Werner
Without knowing what your problem is I would improve the script this way:
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
# Start by copying the old countfile to a new one that will be referenced later
mv /usr/byr/countfile /usr/byr/countfile2
# then pipe the output of the counting of the lines to the countfile
ls -l /usr/byr/ | wc -l | read new
echo $new > /usr/byr/countfile
# assign the variable $new to the current number of lines
# and assign $old to the previous number of lines
cat /usr/byr/countfile2 | read old
echo $new
echo $old
# then compare the value of the old number to the new number
# and write to the testfile a string that will be looked at by NIGHTWATCH
if [ $new -gt $old ]; then
echo ok > /usr/byr/testfile
echo $new
echo $old
echo "ok"
elif [ $new -eq $old ]; then
echo same > /usr/byr/testfile
echo $new
echo $old
echo "same"
else
echo fail > /usr/byr/testfile
echo $new
echo $old
echo "fail"
fi
======
Werner
Tried your mods, but now there is nothing getting written to the countfile.. it is an empty file... new and old are blank lines...
The problem with your:
cut -c 1-8 /usr/byr/countfile > $new
is that this does not assign a value to a variable. It will write the output of the 'cut' command to a file with the name of the string in "new"!
So if "new=xxx"
then the 'cut' output will be written to file 'xxx'.
cut -c 1-8 /usr/byr/countfile > $new
is that this does not assign a value to a variable. It will write the output of the 'cut' command to a file with the name of the string in "new"!
So if "new=xxx"
then the 'cut' output will be written to file 'xxx'.
to Greissh.. each echo was a blank line.. there were no values displayed.
how to I get the value I have stored (string) back and assigned to the varriable $new or $old ??
how to I get the value I have stored (string) back and assigned to the varriable $new or $old ??
What UNIX are you running on? What is your login shell?
If you do a 'read' from the command line and then a 'echo $REPLY', does that work?
If you do a 'read' from the command line and then a 'echo $REPLY', does that work?
SUN OS 5.8 I'm not sure what shell, it is the default...the #!/usr/bin/sh .. at the top seems to work and the script gets processed.
I'm not sure of you read from command line...
If I do a
read countfile
it comes back at a blank line. If I press Enter it comes back to the # prompt. If I then type in echo $REPLY, nothing happens..
I'm not sure of you read from command line...
If I do a
read countfile
it comes back at a blank line. If I press Enter it comes back to the # prompt. If I then type in echo $REPLY, nothing happens..
I did fix part of the problem by declaring where the first countfile should be placed, the read old.. read new... are still coming up blank. htat is the real issue.. how to get the one line from the file into a variable...
Current script is:
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
# Start by copying the old countfile to a new one that will be referenced later
mv /usr/byr/countfile /usr/byr/countfile2
# then pipe the output of the counting of the lines to the countfile
ls -l /usr/byr/ | wc -l > /usr/byr/countfile
# assign the variable $new to the current number of lines
# and assign $old to the previous number of lines
cat /usr/byr/countfile2 | read old
cat /usr/byr/countfile | read new
echo $new
echo $old
# then compare the value of the old number to the new number
# and write to the testfile a string that will be looked at by NIGHTWATCH
if [ exp $new -gt exp $old ]; then
echo ok > /usr/byr/testfile
echo $new
echo $old
echo "ok"
elif [ exp $new -eq exp $old ]; then
echo same > /usr/byr/testfile
echo $new
echo $old
echo "same"
else
echo fail > /usr/byr/testfile
echo $new
echo $old
echo "fail"
fi
Current script is:
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
# Start by copying the old countfile to a new one that will be referenced later
mv /usr/byr/countfile /usr/byr/countfile2
# then pipe the output of the counting of the lines to the countfile
ls -l /usr/byr/ | wc -l > /usr/byr/countfile
# assign the variable $new to the current number of lines
# and assign $old to the previous number of lines
cat /usr/byr/countfile2 | read old
cat /usr/byr/countfile | read new
echo $new
echo $old
# then compare the value of the old number to the new number
# and write to the testfile a string that will be looked at by NIGHTWATCH
if [ exp $new -gt exp $old ]; then
echo ok > /usr/byr/testfile
echo $new
echo $old
echo "ok"
elif [ exp $new -eq exp $old ]; then
echo same > /usr/byr/testfile
echo $new
echo $old
echo "same"
else
echo fail > /usr/byr/testfile
echo $new
echo $old
echo "fail"
fi
Ok, let's try the read again:
run
read
from the command line. You will see an empty line, because the 'read' command is waiting for input. Type
'126' <Enter>
then run
echo $REPLY
You should see the '126' as output. (Do a 'man read' to learn more about the command)
If that works, then do
read line
This will read everything you type until you press the Enter key into the variable 'line'.
echo $line
should show you all your input.
Start a script with:
#!/usr/bin/sh
ls -l /usr/byr/ | wc -l
ls -l /usr/byr/ | wc -l > /usr/byr/countfile
Do you get a number from the first command?
When you do
cat /usr/byr/countfile
is the same number in that file?
run
read
from the command line. You will see an empty line, because the 'read' command is waiting for input. Type
'126' <Enter>
then run
echo $REPLY
You should see the '126' as output. (Do a 'man read' to learn more about the command)
If that works, then do
read line
This will read everything you type until you press the Enter key into the variable 'line'.
echo $line
should show you all your input.
Start a script with:
#!/usr/bin/sh
ls -l /usr/byr/ | wc -l
ls -l /usr/byr/ | wc -l > /usr/byr/countfile
Do you get a number from the first command?
When you do
cat /usr/byr/countfile
is the same number in that file?
First part...
Sun Microsystems Inc. SunOS 5.8 Generic February 2000
# read
read: missing arguments
# read test
126
# echo $REPLY
# read line
this will read everything
# echo nline
nline
# echo $line
this will read everything
#
Results of script is as you list the output is the same as the cat listing
Sun Microsystems Inc. SunOS 5.8 Generic February 2000
# read
read: missing arguments
# read test
126
# echo $REPLY
# read line
this will read everything
# echo nline
nline
# echo $line
this will read everything
#
Results of script is as you list the output is the same as the cat listing
Some more on 'read':
'read' without argument is supposed to read into the variable REPLY. It looks like your version is too old and always needs an argument.
'read line' will read all your input into the variable 'line'.
'echo nline' will just print the string 'nline' to standard out, 'echo $line' will print the CONTENT of 'line' to the output device.
That shows that the 'read' should work.
Next scipt:
#!/usr/bin/sh
#This will show the number of files
ls -l /usr/byr/ | wc -l
#This will read the number of files into the variable 'line'
ls -l /usr/byr/ | wc -l | read line
#This will show the CONTENT of the variable 'line'
echo $line
should produce the same results. What we do in the first line is to pipe the output of the 'wc' command to the 'read' command which will store that number in the 'line' variable. Please make sure that you understand that 'line' and '$line' are different things. ('$line' is the CONTENT of 'line'!)
'read' without argument is supposed to read into the variable REPLY. It looks like your version is too old and always needs an argument.
'read line' will read all your input into the variable 'line'.
'echo nline' will just print the string 'nline' to standard out, 'echo $line' will print the CONTENT of 'line' to the output device.
That shows that the 'read' should work.
Next scipt:
#!/usr/bin/sh
#This will show the number of files
ls -l /usr/byr/ | wc -l
#This will read the number of files into the variable 'line'
ls -l /usr/byr/ | wc -l | read line
#This will show the CONTENT of the variable 'line'
echo $line
should produce the same results. What we do in the first line is to pipe the output of the 'wc' command to the 'read' command which will store that number in the 'line' variable. Please make sure that you understand that 'line' and '$line' are different things. ('$line' is the CONTENT of 'line'!)
what you have given so far works fine... what next to get the variable from the new counted list to the countfile and the countfile2 value back back into the old variable.
Here's how I would write/simplify it:
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count=`ls /usr/byr/ | wc -l`
previous=`grep -c . $countfile`
echo $count >$countfile
if [ $count -gt $previous ]
then
echo ok >$testfile
elif [ $count -eq $previous ]
then
echo same >$testfile
else
echo fail >$testfile
fi
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count=`ls /usr/byr/ | wc -l`
previous=`grep -c . $countfile`
echo $count >$countfile
if [ $count -gt $previous ]
then
echo ok >$testfile
elif [ $count -eq $previous ]
then
echo same >$testfile
else
echo fail >$testfile
fi
Modified the script as listed below and notice that it die not write out the number of lines in the ls -l command.... very odd.
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
# Start by copying the old countfile to a new one that will be referenced later
mv /usr/byr/countfile /usr/byr/countfile2
# then pipe the output of the counting of the lines to the variable new
ls -l /usr/byr/ | wc -l | read new
echo $new
echo "should be new on line above"
# ls -l /usr/byr/ | wc -l > /usr/byr/countfile
# assign the variable $new to the current number of lines
# and assign $old to the previous number of lines
# cat /usr/byr/countfile2 | read old
# cat /usr/byr/countfile | read new
echo $new
echo $old
# then compare the value of the old number to the new number
# and write to the testfile a string that will be looked at by NIGHTWATCH
if [ exp $new -gt exp $old ]; then
echo ok > /usr/byr/testfile
echo $new
echo $old
echo "ok"
elif [ exp $new -eq exp $old ]; then
echo same > /usr/byr/testfile
echo $new
echo $old
"countfile.sh" 40 lines, 1002 characters
# countfile.sh
<<========================
should be new on line above
same
#
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
# Start by copying the old countfile to a new one that will be referenced later
mv /usr/byr/countfile /usr/byr/countfile2
# then pipe the output of the counting of the lines to the variable new
ls -l /usr/byr/ | wc -l | read new
echo $new
echo "should be new on line above"
# ls -l /usr/byr/ | wc -l > /usr/byr/countfile
# assign the variable $new to the current number of lines
# and assign $old to the previous number of lines
# cat /usr/byr/countfile2 | read old
# cat /usr/byr/countfile | read new
echo $new
echo $old
# then compare the value of the old number to the new number
# and write to the testfile a string that will be looked at by NIGHTWATCH
if [ exp $new -gt exp $old ]; then
echo ok > /usr/byr/testfile
echo $new
echo $old
echo "ok"
elif [ exp $new -eq exp $old ]; then
echo same > /usr/byr/testfile
echo $new
echo $old
"countfile.sh" 40 lines, 1002 characters
# countfile.sh
<<========================
should be new on line above
same
#
Tintin did I miss something ?? Here is the script
#!/usr/bin/sh
# Script to count the number of lines from a ls - l command
countfile= /usr/byr/countfile
testfile= /usr/byr/testfile
count= 'ls /usr/byr/ | wc -l'
previous= 'grep -c.#countfile'
#!/usr/bin/sh
# Script to count the number of lines from a ls - l command
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count='ls /usr/byr/ | wc -l'
previous='grep -c.#countfile'
echo $count >$countfile
if [ $count -gt $previous ]
then
echo ok>$testfile
elif [ $count -eq $previous ]
then
echo same >$testfile
else
echo fail >$testfile
fi
Here is the output ?? error
# test.sh
/usr/bin/test.sh: test: unknown operator /usr/byr/
Any ideas ??
#!/usr/bin/sh
# Script to count the number of lines from a ls - l command
countfile= /usr/byr/countfile
testfile= /usr/byr/testfile
count= 'ls /usr/byr/ | wc -l'
previous= 'grep -c.#countfile'
#!/usr/bin/sh
# Script to count the number of lines from a ls - l command
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count='ls /usr/byr/ | wc -l'
previous='grep -c.#countfile'
echo $count >$countfile
if [ $count -gt $previous ]
then
echo ok>$testfile
elif [ $count -eq $previous ]
then
echo same >$testfile
else
echo fail >$testfile
fi
Here is the output ?? error
# test.sh
/usr/bin/test.sh: test: unknown operator /usr/byr/
Any ideas ??
Sorry, a mistake in the logic.
Here is the corrected script (which I've tested on my Solaris server).
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count=`ls /usr/byr | wc -l`
if [ -f $countfile ]
then
previous=`cat $countfile`
else
previous=0
fi
echo $count >$countfile
if [ $count -gt $previous ]
then
echo ok >$testfile
elif [ $count -eq $previous ]
then
echo same >$testfile
else
echo fail >$testfile
fi
Here is the corrected script (which I've tested on my Solaris server).
#!/usr/bin/sh
# Script to count number of lines from the ls - l command
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count=`ls /usr/byr | wc -l`
if [ -f $countfile ]
then
previous=`cat $countfile`
else
previous=0
fi
echo $count >$countfile
if [ $count -gt $previous ]
then
echo ok >$testfile
elif [ $count -eq $previous ]
then
echo same >$testfile
else
echo fail >$testfile
fi
Where id I go wrong ?? ... see error at end
#!/usr/bin/sh
# Script to count the number of lines from a ls - l command
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count='ls /usr/byr | wc -l'
if [ -f $countfile ]
then
previous='cat $countfile'
else
previous = 0
fi
if [ $count -gt $previous ]
then
echo ok>$testfile
elif [ $count -eq $previous ]
then
echo same >$testfile
else
echo fail >$testfile
fi
running results in:
# test.sh
/usr/bin/test.sh: test: unknown operator /usr/byr
#
#!/usr/bin/sh
# Script to count the number of lines from a ls - l command
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count='ls /usr/byr | wc -l'
if [ -f $countfile ]
then
previous='cat $countfile'
else
previous = 0
fi
if [ $count -gt $previous ]
then
echo ok>$testfile
elif [ $count -eq $previous ]
then
echo same >$testfile
else
echo fail >$testfile
fi
running results in:
# test.sh
/usr/bin/test.sh: test: unknown operator /usr/byr
#
Output:
# cd /usr/bin
# sh -x test.sh
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count=ls /usr/byr | wc -l
+ [ -f /usr/byr/countfile ]
previous=cat $countfile
+ [ ls /usr/byr | wc -l -gt cat $countfile ]
test.sh: test: unknown operator /usr/byr
#
# cd /usr/bin
# sh -x test.sh
countfile=/usr/byr/countfi
testfile=/usr/byr/testfile
count=ls /usr/byr | wc -l
+ [ -f /usr/byr/countfile ]
previous=cat $countfile
+ [ ls /usr/byr | wc -l -gt cat $countfile ]
test.sh: test: unknown operator /usr/byr
#
911bob
Unfortunatelly we are working now on two different paths ...
From your last reply I assume that the 'read' worked ...
#!/usr/bin/sh
#This will show the number of files
ls -l /usr/byr/ | wc -l
#This will read the number of files into the variable 'line'
ls -l /usr/byr/ | wc -l | read line1
#This will write the number into a file
ls -l /usr/byr/ | wc -l > countfile
#and read it back in
cat countfile | read line2
#This will show the CONTENT of the variable 'line1' and 'line2'
echo line1="$line1" line2="$line2"
This should show something like
line1=67 line2=67
Let me know what you see ...
Unfortunatelly we are working now on two different paths ...
From your last reply I assume that the 'read' worked ...
#!/usr/bin/sh
#This will show the number of files
ls -l /usr/byr/ | wc -l
#This will read the number of files into the variable 'line'
ls -l /usr/byr/ | wc -l | read line1
#This will write the number into a file
ls -l /usr/byr/ | wc -l > countfile
#and read it back in
cat countfile | read line2
#This will show the CONTENT of the variable 'line1' and 'line2'
echo line1="$line1" line2="$line2"
This should show something like
line1=67 line2=67
Let me know what you see ...
CC Werner, definetely two separate scripts, and two separate problems:-).
Your problem with Tintins perfectly fine scriptlet is the following line:
count='ls /usr/byr | wc -l'
Since you use the wrong kind of quotes you set cout to the string "ls /usr/byr | wc -l" instead of executing those commands and setting it to the result of them.
Note the difference between single quotes ' string ' and back-ticks ` execute commands ` ... So just change that line to
count=`ls /usr/byr | wc -l`
and that script would be fine.
Are we seeing verbatim quotes for the read problem you have with Werners script-variant?
-- Glenn
Your problem with Tintins perfectly fine scriptlet is the following line:
count='ls /usr/byr | wc -l'
Since you use the wrong kind of quotes you set cout to the string "ls /usr/byr | wc -l" instead of executing those commands and setting it to the result of them.
Note the difference between single quotes ' string ' and back-ticks ` execute commands ` ... So just change that line to
count=`ls /usr/byr | wc -l`
and that script would be fine.
Are we seeing verbatim quotes for the read problem you have with Werners script-variant?
-- Glenn
I know you and Tintin are going down two paths.. But I will continue to work with both.. I have 2 test files so i will put yours into one and his into the other. I really appreciate your help.
Script:
ls -l /usr/byr/ | wc -l
ls -l /usr/byr/ | wc -l | read new
ls -l /usr/byr/ | wc -l > countfile
cat countfile | read line2
echo line1="$new" line2="$line2"
output:
# countfile.sh
25
line1= line2=
Result of cat countfile from command prompt:
# cat countfile
25
Very odd it does not seem to wnat to read the variable...
Script:
ls -l /usr/byr/ | wc -l
ls -l /usr/byr/ | wc -l | read new
ls -l /usr/byr/ | wc -l > countfile
cat countfile | read line2
echo line1="$new" line2="$line2"
output:
# countfile.sh
25
line1= line2=
Result of cat countfile from command prompt:
# cat countfile
25
Very odd it does not seem to wnat to read the variable...
Hm, I think the "uncooperativeness of the read command/shell builtin is due to "stupidity" in the /usr/bin/read command, or bourne shell builtin. Switch to korn shell, and Werners script will work too... Do this by changing the
#!/usr/bin/sh
line to
#!/usr/bin/ksh
-- Glenn
#!/usr/bin/sh
line to
#!/usr/bin/ksh
-- Glenn
We dumped our last SunOS machines a year ago, so I can't even check ... but Glenn is right, the 'read' is misbehaving as we see.
Try Glenn's suggestion to switch to ksh if possible ... hopefully you get a better result there.
Try Glenn's suggestion to switch to ksh if possible ... hopefully you get a better result there.
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Learn how to get help with Linux/Unix bash shell commands.
Use help to read help documents for built in bash shell commands.: Use man to interface with the online reference manuals for shell commands.: Use man to search man pages for unknown command…
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