I'm trying to write a simple script that creates five textfiles enumerated by a variable in a loop. Can anybody tell my how to make the arithmetic expression be evaluated. This doesn't seem to work:
touch ~/test$(($i+1)).txt
(I am aware that I could evaluate the expression in a separate statement or change of the loop...)
Thanks in advance!
The correct answer would depend on the shell you're using. It looks a little like bash, but I don't want to make too many assumptions.
The command you list touch ~/test$(($i+1)).txt will correctly touch the file with whatever $i+1 is, but what it's not doing, is changing the value of $i.
What it seems to me like you want to do is:
Find the largest value of n amongst the files named testn.txt where n is a number larger than 0
Increment the number as m.
touch (or otherwise output) to a new file named testm.txt where m is the incremented number.
Using techniques listed here you could strip the parts of the filename to build the value you wanted.
Assume the following was in a file named "touchup.sh":
#!/bin/bash
# first param is the basename of the file (e.g. "~/test")
# second param is the extension of the file (e.g. ".txt")
# assume the files are named so that we can locate via $1*$2 (test*.txt)
largest=0
for candidate in (ls $1*$2); do
intermed=${candidate#$1*}
final=${intermed%%$2}
# don't want to assume that the files are in any specific order by ls
if [[ $final -gt $largest ]]; then
largest=$final
fi
done
# Now, increment and output.
largest=$(($largest+1))
touch $1$largest$2
Related
I have a script that I call with an application, I can't run it from command line. I derive the directory where the script is called and in the next variable go up 1 level where my files are stored. From there I have 3 variables with the full path and file names (with wildcard), which I will refer to as "masks".
I need to find and "do something with" (copy/write their names to a new file, whatever else) to each of these masks. The do something part isn't my obstacle as I've done this fine when I'm working with a single mask, but I would like to do it cleanly in a single loop instead of duplicating loop and just referencing each mask separately if possible.
Assume in my $FILESFOLDER directory below that I have 2 existing files, aaa0.csv & bbb0.csv, but no file matching the ccc*.csv mask.
#!/bin/bash
SCRIPTFOLDER=${0%/*}
FILESFOLDER="$(dirname "$SCRIPTFOLDER")"
ARCHIVEFOLDER="$FILESFOLDER"/archive
LOGFILE="$SCRIPTFOLDER"/log.txt
FILES1="$FILESFOLDER"/"aaa*.csv"
FILES2="$FILESFOLDER"/"bbb*.csv"
FILES3="$FILESFOLDER"/"ccc*.csv"
ALLFILES="$FILES1
$FILES2
$FILES3"
#here as an example I would like to do a loop through $ALLFILES and copy anything that matches to $ARCHIVEFOLDER.
for f in $ALLFILES; do
cp -v "$f" "$ARCHIVEFOLDER" > "$LOGFILE"
done
echo "$ALLFILES" >> "$LOGFILE"
The thing that really spins my head is when I run something like this (I haven't done it with the copy command in place) that log file at the end shows:
filesfolder/aaa0.csv filesfolder/bbb0.csv filesfolder/ccc*.csv
Where I would expect echoing $ALLFILES just to show me the masks
filesfolder/aaa*.csv filesfolder/bbb*.csv filesfolder/ccc*.csv
In my "do something" area, I need to be able to use whatever method to find the files by their full path/name with the wildcard if at all possible. Sometimes my network is down for maintenance and I don't want to risk failing a change directory. I rarely work in linux (primarily SQL background) so feel free to poke holes in everything I've done wrong. Thanks in advance!
Here's a light refactoring with significantly fewer distracting variables.
#!/bin/bash
script=${0%/*}
folder="$(dirname "$script")"
archive="$folder"/archive
log="$folder"/log.txt # you would certainly want this in the folder, not $script/log.txt
shopt -s nullglob
all=()
for prefix in aaa bbb ccc; do
cp -v "$folder/$prefix"*.csv "$archive" >>"$log" # append, don't overwrite
all+=("$folder/$prefix"*.csv)
done
echo "${all[#]}" >> "$log"
The change in the loop to append the output or cp -v instead of overwrite is a bug fix; otherwise the log would only contain the output from the last loop iteration.
I would probably prefer to have the files echoed from inside the loop as well, one per line, instead of collect them all on one humongous line. Then you can remove the array all and instead simply
printf '%s\n' "$folder/$prefix"*.csv >>"$log"
shopt -s nullglob is a Bash extension (so won't work with sh) which says to discard any wildcard which doesn't match any files (the default behavior is to leave globs unexpanded if they don't match anything). If you want a different solution, perhaps see Test whether a glob has any matches in Bash
You should use lower case for your private variables so I changed that, too. Notice also how the script variable doesn't actually contain a folder name (or "directory" as we adults prefer to call it); fixing that uncovered a bug in your attempt.
If your wildcards are more complex, you might want to create an array for each pattern.
tmpspaces=(/tmp/*\ *)
homequest=($HOME/*\?*)
for file in "${tmpspaces[#]}" "${homequest[#]}"; do
: stuff with "$file", with proper quoting
done
The only robust way to handle file names which could contain shell metacharacters is to use an array variable; using string variables for file names is notoriously brittle.
Perhaps see also https://mywiki.wooledge.org/BashFAQ/020
Its my first time to use BASH scripting and been looking to some tutorials but cant figure out some codes. I just want to list all the files in a folder, but i cant do it.
Heres my code so far.
#!/bin/bash
# My first script
echo "Printing files..."
FILES="/Bash/sample/*"
for f in $FILES
do
echo "this is $f"
done
and here is my output..
Printing files...
this is /Bash/sample/*
What is wrong with my code?
You misunderstood what bash means by the word "in". The statement for f in $FILES simply iterates over (space-delimited) words in the string $FILES, whose value is "/Bash/sample" (one word). You seemingly want the files that are "in" the named directory, a spatial metaphor that bash's syntax doesn't assume, so you would have to explicitly tell it to list the files.
for f in `ls $FILES` # illustrates the problem - but don't actually do this (see below)
...
might do it. This converts the output of the ls command into a string, "in" which there will be one word per file.
NB: this example is to help understand what "in" means but is not a good general solution. It will run into trouble as soon as one of the files has a space in its name—such files will contribute two or more words to the list, each of which taken alone may not be a valid filename. This highlights (a) that you should always take extra steps to program around the whitespace problem in bash and similar shells, and (b) that you should avoid spaces in your own file and directory names, because you'll come across plenty of otherwise useful third-party scripts and utilities that have not made the effort to comply with (a). Unfortunately, proper compliance can often lead to quite obfuscated syntax in bash.
I think problem in path "/Bash/sample/*".
U need change this location to absolute, for example:
/home/username/Bash/sample/*
Or use relative path, for example:
~/Bash/sample/*
On most systems this is fully equivalent for:
/home/username/Bash/sample/*
Where username is your current username, use whoami to see your current username.
Best place for learning Bash: http://www.tldp.org/LDP/abs/html/index.html
This should work:
echo "Printing files..."
FILES=(/Bash/sample/*) # create an array.
# Works with filenames containing spaces.
# String variable does not work for that case.
for f in "${FILES[#]}" # iterate over the array.
do
echo "this is $f"
done
& you should not parse ls output.
Take a list of your files)
If you want to take list of your files and see them:
ls ###Takes list###
ls -sh ###Takes list + File size###
...
If you want to send list of files to a file to read and check them later:
ls > FileName.Format ###Takes list and sends them to a file###
ls > FileName.Format ###Takes list with file size and sends them to a file###
I am trying to write a bash script which allows me to automate the creation of multiple directories with incrementing names.
For example, I am trying to create the directories named v0v1, v1v2, ... , v40v41.
I have tried using a 'for' loop, where I create a variable and set this to be equal to the current value of i+1 (where 'i' is the current loop iteration), but it is not working as expected.
I have managed to get the variable to increment (and have checked this using 'echo'), but I cannot get it to become part of the new directory name.
The code I have written is as follows:
for i in {0..40}; do let r=$((i+1)); mkdir v$iv$r; done
However, the directories produced have names only containing the first variable value (i.e. v0, v1, ..., v40), and do not include the 'v$r' at all.
Does anyone have any ideas how to use two variables at once in the same filename?
printf 'r=%d ; mkdir v$((r-1))v${r} ;' $(seq 2 41) |sh
You don't need a shell loop at all.
for i in {0..40}; do let r=$((i+1)); mkdir v${i}v$r; done
When bash sees the expression v$iv$r, it substitutes in for variables iv and r. But, of course, there is no iv. So bash substitutes in the empty string. The solution is to use braces to assure that bash knows where the variable name ends. Thus: v${i}v$r.
I'm dealing with a pipeline of predominantly shell and Perl files, all of which pass parameters (paths) to the next. I decided it would be better to use a single file to store all the paths and just call that for every file. The issue is I am using awk to grab the files at the beginning of each file, and it's turning out to be a lot of repetition.
My question is: I do not know if there is a way to store key-value pairs in a file so shell can natively do something with the key and return the value? It needs to access an external file, because the pipeline uses many scripts and a map in a specific file would result in parameters being passed everywhere. Is there some little quirk I do not know of that performs a map function on an external file?
You can make a file of env var assignments and source that file as need, ie.
$ cat myEnvFile
path1=/x/y/z
path2=/w/xy
path3=/r/s/t
otherOpt1="-x"
Inside your script you can source with either . myEnvFile or the more versbose version of the same feature sourc myEnvFile (assuming bash shell) , i.e.
$cat myScript
#!/bin/bash
. /path/to/myEnvFile
# main logic below
....
# references to defined var
if [[ -d $path2 ]] ; then
cd $path2
else
echo "no pa4h2=$path2 found, can't continue" 1>&1
exit 1
fi
Based on how you've described your problem this should work well, and provide a-one-stop-shop for all of your variable settings.
IHTH
In bash, there's mapfile, but that reads the lines of a file into a numerically-indexed array. To read a whitespace-separated file into an associative array, I would
declare -A map
while read key value; do
map[$key]=$value
done < filename
However this sounds like an XY problem. Can you give us an example (in code) of what you're actually doing? When I see long piplines of grep|awk|sed, there's usually a way to simplify. For example, is passing data by parameters better than passing via stdout|stdin?
In other words, I'm questioning your statement "I decided it would be better..."
I know this question has been asked, but I can't find more than one solution, and it does not work for me. Essentially, I'm looking for a bash script that will take a file list that looks like this:
image1.jpg
image2.jpg
image3.jpg
And then make a copy of each one, but number it sequentially backwards. So, the sequence would have three new files created, being:
image4.jpg
image5.jpg
image6.jpg
And yet, image4.jpg would have been an untouched copy of image3.jpg, and image5.jpg an untouched copy of image2.jpg, and so on. I have already tried the solution outlined in this stackoverflow question with no luck. I am admittedly not very far down the bash scripting path, and if I take the chunk of code in the first listed answer and make a script, I always get "2: Syntax error: "(" unexpected" over and over. I've tried changing the syntax with the ( around a bit, but no success ever. So, either I am doing something wrong or there's a better script around.
Sorry for not posting this earlier, but the code I'm using is:
image=( image*.jpg )
MAX=${#image[*]}
for i in ${image[*]}
do
num=${i:5:3} # grab the digits
compliment=$(printf '%03d' $(echo $MAX-$num | bc))
ln $i copy_of_image$compliment.jpg
done
And I'm taking this code and pasting it into a file with nano, and adding !#/bin/bash as the first line, then chmod +x script and executing in bash via sh script. Of course, in my test runs, I'm using files appropriately titled image1.jpg - but I was also wondering about a way to apply this script to a directory of jpegs, not necessarily titled image(integer).jpg - in my file keeping structure, most of these are a single word, followed by a number, then .jpg, and it would be nice to not have to rewrite the script for each use.
Perhaps something like this. It will work well for something like script image*.jpg where the wildcard matches a set of files which match a regular pattern with monotonously increasing numbers of the same length, and less ideally with a less regular subset of the files in the current directory. It simply assumes that the last file's digit index plus one through the total number of file names is the range of digits to loop over.
#!/bin/sh
# Extract number from final file name
eval lastidx=\$$#
tmp=${lastidx#*[!0-9][0-9]}
lastidx=${lastidx#${lastidx%[0-9]$tmp}}
tmp=${lastidx%[0-9][!0-9]*}
lastidx=${lastidx%${lastidx#$tmp[0-9]}}
num=$(expr $lastidx + $#)
width=${#lastidx}
for f; do
pref=${f%%[0-9]*}
suff=${f##*[0-9]}
# Maybe show a warning if pref, suff, or width changed since the previous file
printf "cp '$f' '$pref%0${width}i$suff'\\n" $num
num=$(expr $num - 1)
done |
sh
This is sh-compatible; the expr stuff and the substring extraction up front is ugly but Bourne-compatible. If you are fine with the built-in arithmetic and string manipulation constructs of Bash, converting to that form should be trivial.
(To be explicit, ${var%foo} returns the value of $var with foo trimmed off the end, and ${var#foo} does similar trimming from the beginning of the value. Regular shell wildcard matching operators are available in the expression for what to trim. ${#var} returns the length of the value of $var.)
Maybe your real test data runs from 001 to 300, but here you have image1 2 3, and therefore you extract one, not three digits from the filename. num=${i:5:1}
Integer arithmetic can be done in the bash without calling bc
${#image[#]} is more robust than ${#image[*]}, but shouldn't be a difference here.
I didn't consult a dictionary, but isn't compliment something for your girl friend? The opposite is complement, isn't it? :)
the other command made links - to make copies, call cp.
Code:
#!/bin/bash
image=( image*.jpg )
MAX=${#image[#]}
for i in ${image[#]}
do
num=${i:5:1}
complement=$((2*$MAX-$num+1))
cp $i image$complement.jpg
done
Most important: If it is bash, call it with bash. Best: do a shebang (as you did), make it executable and call it by ./name . Calling it with sh name will force the wrong interpreter. If you don't make it executable, call it bash name.