I have a js script that converts kml location history files to csv. I wrote a bash script to loop through all the files in a directory. The script works when I execute it from command line ./index.js filename.kml > filename.csv
But nothing happens when I execute the bash file that is supposed to loop through all files.
I know it probably is a simple mistake but I can't spot it.
#!/bin/bash
# file: foo.sh
for f in *.kml; do
test -e "${f%.kml}" && continue
./index.js "$f" > "-fcsv"
done
Just delete the "&& continue", if I'm not wrong you're skipping the current iteration with the "continue" keyword, that's why nothing happens
EDIT
Also, you shouldn't test if the file exists, the for loop is enough to be sure that "f" will be a valid .kml file. Anyways, if you still want to do it you have to do it like:
#!/bin/bash
# file: foo.sh
for f in *.kml; do
if [ -e "$f" ]; then
./index.js "$f" > "$f.csv"
fi;
done
Related
My requirement is to replace file only when it is not being accessed. I have following snippet:
if [ -f file ]
then
while true
do
if [ -n "$(fuser "file")" ]
then
echo "file is in use..."
else
echo "file is free..."
break
fi
done
fi
{
flock -x 3
mv newfile file
} 3>file
But I have a doubt that I am not handling concurrency properly. Please give some insights and possible way to achieve this.
Thanks.
My requirement is to replace file only when it is not being accessed.
Getting requirements right can be hard. In case your actual requirement is the following, you can boil down the whole script to just one command.
My guess on the actual requirement (not as strict as the original):
Replace file without disturbing any programs reading/writing file.
If this is the case, you can use a very neat behavior: In Unix-like systems file descriptors always point to the file (not path) for which they where opened. You can move or even delete the corresponding path. See also How do the UNIX commands mv and rm work with open files?.
Example:
Open a terminal and enter
i=1; while true; do echo $((i++)); sleep 1; done > file &
tail -f file
The first command writes output to file and runs in the background. The second command reads the file and continues to print its changing content.
Open another terminal and move or delete file, for instance with
mv file file2
echo overwritten > otherFile
mv otherFile file2
rm file2
echo overwritten > file
echo overwritten > file2
While executing these commands have a look at the output of tail -f in the first terminal – it won't be affected by any of these commands. You will never see overwritten.
Solution For New Requirement:
Because of this behavior you can replace the whole script with just one mv command:
mv newfile file
Consider lsof.
mvWhenClear() {
while [[ -f "$1" ]] && lsof "$1"
do sleep $delay
done
mv "$1" "$2" # still allows race condition
}
I am working on some stuff where I am storing data in a file.
But each time I run the script it gets appended to the previous file.
I want help on how I can remove the file if it already exists.
Don't bother checking if the file exists, just try to remove it.
rm -f /p/a/t/h
# or
rm /p/a/t/h 2> /dev/null
Note that the second command will fail (return a non-zero exit status) if the file did not exist, but the first will succeed owing to the -f (short for --force) option. Depending on the situation, this may be an important detail.
But more likely, if you are appending to the file it is because your script is using >> to redirect something into the file. Just replace >> with >. It's hard to say since you've provided no code.
Note that you can do something like test -f /p/a/t/h && rm /p/a/t/h, but doing so is completely pointless. It is quite possible that the test will return true but the /p/a/t/h will fail to exist before you try to remove it, or worse the test will fail and the /p/a/t/h will be created before you execute the next command which expects it to not exist. Attempting this is a classic race condition. Don't do it.
Another one line command I used is:
[ -e file ] && rm file
You can use this:
#!/bin/bash
file="file_you_want_to_delete"
if [ -f "$file" ] ; then
rm "$file"
fi
If you want to ignore the step to check if file exists or not, then you can use a fairly easy command, which will delete the file if exists and does not throw an error if it is non-existing.
rm -f xyz.csv
A one liner shell script to remove a file if it already exist (based on Jindra Helcl's answer):
[ -f file ] && rm file
or with a variable:
#!/bin/bash
file="/path/to/file.ext"
[ -f $file ] && rm $file
Something like this would work
#!/bin/sh
if [ -fe FILE ]
then
rm FILE
fi
-f checks if it's a regular file
-e checks if the file exist
Introduction to if for more information
EDIT : -e used with -f is redundant, fo using -f alone should work too
if [ $( ls <file> ) ]; then rm <file>; fi
Also, if you redirect your output with > instead of >> it will overwrite the previous file
So in my case I wanted to remove a FIFO file before I create it again, so this worked for me:
#!/bin/bash
file="/tmp/test"
rm -rf $file | true
mkfifo $file
| true will continue the script even if file is not found.
I needed to convert several pnm image files to jpeg with pnmtojpeg. So I used this script, which I named 'pnm2jpg':
for f in *.pnm;
do pnmtojpeg -quality=85 "$f" > "${f%.pnm}.jpg";
done
This works very nicely. However, I would like to adapt it further so that it can be used for a single file as well.
In other words, if no files are specified in the command line, then process all the files.
$ pnm2jpg thisfile.pnm # Process only this file.
$ pnm2jpg # Process all pnm files in the current directory.
Your insight is greatly appreciated- Thank you.
Something like:
#!/bin/bash
if [[ -z "$1" ]]; then
for f in *.pnm; do
pnmtojpeg -quality=85 "$f" > "${f%.pnm}.jpg"
done
else
pnmtojpeg -quality=85 "$1" > "${1%.pnm}.jpg"
fi
If you execute pnm2jpg without an argument the if block is processed.
if you execute pnm2jpg thisfile.pnm the else block is processed.
Is it possible to resave the running bash script?
I am running a loop in the bash file to do certain operations. After the execution of operations are completed, I want to resave the current bash file without adding any extra code. I just want the file last modified date to be changed.
Current code run.sh looks something like
#!/bin/bash
FILES=/home/shell/test/*
for f in $FILES
do
if [[ "$f" != *\.* ]]
then
DO STUFF
fi
done
After done, I want run.sh to have current date and possible to do this internally?
You can use the touch command in your script:
touch "$0"
I'm trying to get the contents of a directory using shell script.
My script is:
for entry in `ls`; do
echo $entry
done
However, my current directory contains many files with whitespaces in their names. In that case, this script fails.
What is the correct way to loop over the contents of a directory in shell scripting?
PS: I use bash.
for entry in *
do
echo "$entry"
done
don't parse directory contents using ls in a for loop. you will encounter white space problems. use shell expansion instead
for file in *
do
if [ -f "$file" ];then
echo "$file"
fi
done