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--- linux:bash_snippets [2015/05/11 22:56]
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+====== Bash Snippets ======
+This page contains a collection of useful shell / bash scripting snippets. For a general introduction see [[linux:bash|this page]].
+===== Date / Time =====
+==== Convert UNIX timestamps to human-readable date ====
+<code bash>
+date -d @1278923870 # Mon Jul 12 10:37:50 CEST 2010
+</code>
+==== Date loop ====
+<code>
+ for i in `seq -w 1 31`; do ./myscript 2007-08-$i; done
+</code>
+You can use inner loops for month and year of course.
+===== File Juggling =====
+==== Recursively count number of files in directory ====
+<code bash>
+find DIRECTORY -type f -print | wc -l
+</code>
+==== Parse a Logfile ====
+<code bash>
+  cat $1 | while read line; do
+     sectionId=`echo $line | grep -o "[0-9]\{4\}-[0-9]\{4\}"`
+     statusString=`echo $line | grep -o  "auf .*$"`
+       case $statusString in
+        auf\ FREI )
+        STATUS=1;;
+        auf\ DICHT )
+        STATUS=2;;
+        auf\ STOCKEND )
+        STATUS=3;;
+        auf\ STAU )
+        STATUS=4;;
+        auf\ NICHT\ VERFÜGBAR )
+        STATUS=5;;
+     esac
+     NEWLINE="${line};${sectionId};${STATUS}"
+     echo $NEWLINE >> out.txt
+  done
+</code>
+==== Make a tar'ed archive from selected files ====
+<code bash>
+# starting from current directory, recursively tar and compress everything NOT ending with .csv
+tar cfvz  output.tar.gz * --exclude "*.csv"
+</code>
+==== Remove empty lines from text ====
+<code>
+ grep -v '^$' input.txt > output.txt
+</code>
+Or
+<code>
+ sed -i '/^$/d' input.txt
+</code>
+===== Remove newlines from text =====
+<code>
+ tr "\n" " " input.txt
+</code>
+==== Renaming Stuff ====
+Use the "rename" program.
+<code bash>
+rename 's/\.bak$//' *.bak # removes the .bak suffix from all files matching *.bak
+</code>
+=== Change suffix for multiple files in a directory ===
+*.hh -> *.h
+<code bash>
+rename 's/\.hh/.h/' *.hh
+</code>
+=== Change name for multiple files in a directory ===
+XML taxi files from heedfled have syntax of webservices as name:
+  * First step:
+<code bash>
+     rename -n s/.*Start=// FCD*
+</code>
+  * Second step:
+<code bash>
+      rename -n s/T.*// 2007*
+</code>
+NOTE: remove -n (=no-act) to run the rename
+=== Dry run ===
+Run your rename with -n to see which files would be renamed.
+===== Finding Stuff =====
+==== Find a file ====
+<code bash>
+  find / -name <fieename>
+</code>
+==== Find files with time restriction ====
+Find files older than 10 minutes.
+<code bash>
+  find /path/to/dir -mmin +10
+</code>
+Find files younger than 10 minutes
+<code bash>
+  find /path/to/dir -mmin -10
+</code>
+Other options
+  * -ctime
+  * -mtime
+  * -atime
+  * .. (see man page)
+==== Delete Files Older than 15 days ====
+<code bash>
+  find /path/to/dir -mtime +15 -delete
+</code>
+==== Execute a command on every found file ====
+<code bash>
+  find / -name muh.txt  -exec cat '{}' \;
+</code>
+Multiple -exec switches can be used to execute more commands on one file:
+<code bash>
+  find / -name muh.txt -exec echo '{}' \;  -exec cat '{}' \;
+</code>
+===== EXIF =====
+Exchangeable Image File Format
+=== Adjust EXIF information ===
+<code bash>
+# adjust date/time of exiv tag
+exiv2 image.jpg              # print exiv data
+exiv2 -a 0:42 image.jpg      # add 42 minutes to image timestamp
+exiv2 -a -1:10 image.jpg     # subtract 1 hour 10 minutes from image timestamp
+</code>
+=== Retrieve GPS locations ===
+<code bash>
+exiftool -n -p '$gpslatitude, $gpslongitude, $gpsdatetime' image.jpg
+</code>
+=== Rename file according to EXIV timestamp ===
+Simple rename:
+<code>
+exiftool '-FileName<CreateDate' -d '%Y-%m-%d_%H-%M-%S%%-c.%%le' image.jpg
+</code>
+Rename and rotate:
+<code bash>
+renrot -n %Y-%m-%d_%H-%M-%S image.jpg
+</code>
+===== PDF =====
+=== Shrink pdf files ===
+Compresses the images in a pdf to a reasonable size (but still useful for printing)
+<code bash>
+gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/preprint -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf
+</code>
+See also http://www.ghostscript.com/doc/9.05/Ps2pdf.htm#Options

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