What is sh? sh (or the Shell Command Language) is a programming language described by the POSIX standard. It has many implementations (ksh88, Dash, …). Bash can also be considered an implementation of sh (see below). Because sh is a specification, not an implementation, /bin/sh is a symlink (or a hard link) to an actual … Read more
The simplest and most widely available method to get user input at a shell prompt is the read command. The best way to illustrate its use is a simple demonstration: while true; do read -p “Do you wish to install this program? ” yn case $yn in [Yy]* ) make install; break;; [Nn]* ) exit;; … Read more
It is: if [ $# -eq 0 ] then echo “No arguments supplied” fi The $# variable will tell you the number of input arguments the script was passed. Or you can check if an argument is an empty string or not like: if [ -z “$1” ] then echo “No argument supplied” fi The … Read more
cmd >>file.txt 2>&1 Bash executes the redirects from left to right as follows: >>file.txt: Open file.txt in append mode and redirect stdout there. 2>&1: Redirect stderr to “where stdout is currently going”. In this case, that is a file opened in append mode. In other words, the &1 reuses the file descriptor which stdout currently … Read more
One way to do it is: while read p; do echo “$p” done <peptides.txt As pointed out in the comments, this has the side effects of trimming leading whitespace, interpreting backslash sequences, and skipping the last line if it’s missing a terminating linefeed. If these are concerns, you can do: while IFS=”” read -r p … Read more
Try: find . -name ‘*.php’ | xargs wc -l or (when file names include special characters such as spaces) find . -name ‘*.php’ | sed ‘s/.*/”&”/’ | xargs wc -l The SLOCCount tool may help as well. It will give an accurate source lines of code count for whatever hierarchy you point it at, as … Read more
for i in $(seq 1 $END); do echo $i; done edit: I prefer seq over the other methods because I can actually remember it 😉
You can use it like this: ## declare an array variable declare -a arr=(“element1” “element2” “element3”) ## now loop through the above array for i in “${arr[@]}” do echo “$i” # or do whatever with individual element of the array done # You can access them using echo “${arr[0]}”, “${arr[1]}” also Also works for multi-line … Read more
You can enter the long form command: source ~/.bashrc or you can use the shorter version of the command: . ~/.bashrc
(Usually) The right way if [ -z ${var+x} ]; then echo “var is unset”; else echo “var is set to ‘$var'”; fi where ${var+x} is a parameter expansion which evaluates to nothing if var is unset, and substitutes the string x otherwise. Quotes Digression Quotes can be omitted (so we can say ${var+x} instead of … Read more