I have a bash script that has an if-then-fi statement included. the code block executes only when the XLS is not empty. Currently i'm evaluating this by utilizing the following:
FILESIZE = `wc -c < $FILENAME`
it seems that the default filesize generated is 4096 bytes if the file is empty. So...
if [ $FILESIZE -gt "4096" ]; then
do something
fi
however, my boss isn't a huge fan of hard coded numbers. is there an alternative solution to seeing whether an XLS has data?
thanks!
if [ -r "$FILENAME ] # If there is a readable file "$FILENAME"
then
if [ -s "$FILENAME" ] # If file "$FILENAME" has a size greater than zero bytes
then
do something
fi
fi
You could to use xls2csv command, if result is 0 the file is empty.
xls2csv file.xls | wc -l
This command it's usually in the "catdoc" package.
Related
I am looking to create a bash script that keeps checking a file in directory and perform certain operation on it. I am using while loop, if file does not exists I want that while loop stays quite and keeps on checking condition. Here is what i created but it keeps throwing error that file not found, if file is not there.
while [ ! -f /home/master/applications/tmp/mydata.txt ]
do
cat mydata.txt;
rm mydata.txt;
sleep 1; done
There are two issue in your implementation:
You should use the same (absolute or relative) path in your while loop test statement [ ! -f $file ] and in your cat and rm commands.
The cat command is looking for the file in the current working directory (pwd) and your while statement might be looking somewhere else and hence, your implementation is buggy and won't work as expected if your pwd isn't /home/master/applications/tmp.
You need to move your cat command and rm command after the while block. It doesn't make sense to cat a file if a file doesn't exist. I think your misplaced those commands.
Try this:
file="/home/master/applications/tmp/mydata.txt"
while [ ! -f "$file" ]
do
sleep 1
done
cat $file
rm $file
EDIT
As per suggestion from #Ivan, you could use until instead of while as it suits more to your requirements.
file="/home/master/applications/tmp/mydata.txt"
until [ -f "$file" ]; do sleep 1; done
cat $file
rm $file
Making a different assumption than abhiarora, I'll guess maybe you meant for the file to reappear, and you want it shown each time.
file=/home/master/applications/tmp/mydata.txt
while :
do if [[ -f "$file" ]]
then echo "$(<"$file")"
rm "$file"
fi
sleep 1
done
This creates an infinite loop. If that's NOT what you wanted, use abhiarora's solution.
I have people uploading files to a directory on my Ubuntu Server.
I need to move those files to the final location (another directory) only when I know these files are fully uploaded.
Here's my script so far:
#!/bin/bash
cd /var/uploaded_by_users
for filename in *; do
lsof $filename
if [ -z $? ]; then
# file has been closed, move it
else
echo "*** File is open. Skipping..."
fi
done
cd -
However it's not working as it says some files are open when that's not true. I supposed $? would have 0 if the file was closed and 1 if it wasn't but I think that's wrong.
I'm not linux expert so I'm looking to know how to implement this simple script that will run on a cron job every 1 minute.
[ -z $? ] checks if $? is of zero length or not. Since $? will never be a null string, your check will always fail and result in else part being executed.
You need to test for numeric zero, as below:
lsof "$filename" >/dev/null; lsof_status=$?
if [ "$lsof_status" -eq 0 ]; then
# file is open, skipping
else
# move it
fi
Or more simply (as Benjamin pointed out):
if lsof "$filename" >/dev/null; then
# file is open, skip
else
# move it
fi
Using negation, we can shorten the if statement (as dimo414 pointed out):
if ! lsof "$filename" >/dev/null; then
# move it
fi
You can shorten it even further, using &&:
for filename in *; do
lsof "$filename" >/dev/null && continue # skip if the file is open
# move the file
done
You may not need to worry about when the write is complete, if you are moving the file to a different location in the same file system. As long as the client is using the same file descriptor to write to the file, you can simply create a new hard link for the upload file, then remove the original link. The client's file descriptor won't be affected by one of the links being removed.
cd /var/uploaded_by_users
for f in *; do
ln "$f" /somewhere/else/"$f"
rm "$f"
done
file=/root/stacktrace.log
minsize=100
filesize=$(wc -c <"$file")
echo $filesize
if [ $filesize -ge $minsize ]; then
mailx -s 'File size is more than 10MB' example#gmail.com < /dev/null
fi
Above script is working fine in centos. But its not working in solaris os.
Please help me on this.
Try this:
file=/root/stacktrace.log
maxsize=100
if [ -f "$file" ] && [ -n "$(find "$file" -size +"$maxsize"c)" ]; then
mailx -s "File size is more than $maxsize" example#gmail.com < /dev/null
fi
This uses find to determine that the size is $maxsize or larger, in this case 100 bytes. I also required [ -f "$file" ] to ensure we're looking at a file rather than a directory so find's recursive search won't find a file inside that directory's structure that is sufficiently large.
BSD find and GNU find (but not Solaris find) support better units than just c for "characters" (bytes). Try k, M, or G like -size +"$maxsize"M or else -size +$((maxsize*1048576))c
(Never mind that the syntax highlighting looks odd. You are allowed to nest one level of double quotes inside a "$(…)" command substitution.)
I apologize if this is a trivial question. I am learning how to use linux bash and this little task is giving me a headache...
So I need to write a script, let's call it count.sh. I want that: for each file in the working directory, prints the filename, the number of lines, and the number of words to the console:
test.txt 100 1023
someOtherfiles 10 233
So far, I know that the following gives me all the files names in the directory. And thanks for all who helped me, I get this working version:
for f in *; do
echo -n "$f"
cat "$f" | wc -wl
done
I would really appreciate your help! Thanks ahead!
P.s. If you know great resources (links for tutorials) for learning about script and you are willing to share it with me. I think I really need to know these basics. Thanks again!
If you must have the file name as the first field in your output, try this:
for f in *; do
if [ -f "$f" ]; then
echo -n "$f"
cat "$f" | wc -wl
fi
done
for f in *; do
if [[ -f $f ]]; then
echo "$f $(wc -wl < "$f")"
fi
done
[[ -f $f ]] processes only files (excludes subdirectories) and also handles the case where the directory is empty (in which case * is (by default) left unexpanded, i.e. assigned to $f as is).
echo "$f $(wc -wl < "$f")" uses command substitution ($( ... )) to directly include the output from the enclosed command in the output string passed to echo.
Note that the reason that < is used to direct the content of file $f to wc via stdin is that wc would otherwise append the name of the input file to its output (thanks, #R Sahu).
I have a bash program that will write to an output file. This file may or may not exist, but the script must check permissions and fail early. I can't find an elegant way to make this happen. Here's what I have tried.
set +e
touch $file
set -e
if [ $? -ne 0 ]; then exit;fi
I keep set -e on for this script so it fails if there is ever an error on any line. Is there an easier way to do the above script?
Why complicate things?
file=exists_and_writeable
if [ ! -e "$file" ] ; then
touch "$file"
fi
if [ ! -w "$file" ] ; then
echo cannot write to $file
exit 1
fi
Or, more concisely,
( [ -e "$file" ] || touch "$file" ) && [ ! -w "$file" ] && echo cannot write to $file && exit 1
Rather than check $? on a different line, check the return value immediately like this:
touch file || exit
As long as your umask doesn't restrict the write bit from being set, you can just rely on the return value of touch
You can use -w to check if a file is writable (search for it in the bash man page).
if [[ ! -w $file ]]; then exit; fi
Why must the script fail early? By separating the writable test and the file open() you introduce a race condition. Instead, why not try to open (truncate/append) the file for writing, and deal with the error if it occurs? Something like:
$ echo foo > output.txt
$ if [ $? -ne 0 ]; then die("Couldn't echo foo")
As others mention, the "noclobber" option might be useful if you want to avoid overwriting existing files.
Open the file for writing. In the shell, this is done with an output redirection. You can redirect the shell's standard output by putting the redirection on the exec built-in with no argument.
set -e
exec >shell.out # exit if shell.out can't be opened
echo "This will appear in shell.out"
Make sure you haven't set the noclobber option (which is useful interactively but often unusable in scripts). Use > if you want to truncate the file if it exists, and >> if you want to append instead.
If you only want to test permissions, you can run : >foo.out to create the file (or truncate it if it exists).
If you only want some commands to write to the file, open it on some other descriptor, then redirect as needed.
set -e
exec 3>foo.out
echo "This will appear on the standard output"
echo >&3 "This will appear in foo.out"
echo "This will appear both on standard output and in foo.out" | tee /dev/fd/3
(/dev/fd is not supported everywhere; it's available at least on Linux, *BSD, Solaris and Cygwin.)