Shell Tricks

程序设计

Iterate in 2 files

while read i <&3 && read j <&4; do
    # op $i $j
done 3<$IFILE 4<&JFILE

Every 3 line

awk 'NR % 3 == 0' myfile

Be careful with lasting backslash

caffe train solver.prototxt
    --weights=iter_1000.caffemodel

It will be executed! And finally you will find out caffe didn't load any thing!

List full path

ls -d -1 ${PWD}/dir

Find out intersectino

sort f1 f2 | uniq -d

Wait for children

for job in `jobs -p`; do
    wait $job
done

Conditional execution

if [[ ${#FILES} -le $THREDHOLD ]]; then
    # ...
else
    # ...
fi

Use -e to test if a file exists.

Brackets

$(cmd) to execute cmd, $((j + i)) to execute expression, ${var} to expand variables.

Glob strip

# Strip prefix (greedy)
filename=${VARIABLE_NAME##PREFIX}
# Strip postfix (non-greedy)
dirname=${VARIABLE_NAME%POSTFIX}

Merge 2 files line by line

paste f1 f2