for

Loop command.

Syntax
      for name [in words ...]; do commands; done

Expand words, and execute commands once for each member in the resultant list, with name bound to the current member.

If `in words' is not present, the for command executes the commands once for each positional parameter that is set, as if `in "$@"' had been specified (see section Special Parameters). The return status is the exit status of the last command that executes. If there are no items in the expansion of words, no commands are executed, and the return status is zero. An alternate form of the for command is also supported:

for (( expr1 ; expr2 ; expr3 )) ; do commands ; done

First, the arithmetic expression expr1 is evaluated according to the rules described below . The arithmetic expression expr2 is then evaluated repeatedly until it evaluates to zero.

Each time expr2 evaluates to a non-zero value, commands are executed and the arithmetic expression expr3 is evaluated. If any expression is omitted, it behaves as if it evaluates to 1.

The return value is the exit status of the last command in list that is executed, or false if any of the expressions is invalid.

for is a bash builtin command

Examples

#! /bin/bash
# List of manufacturers
for manufacturer in Apple Sony "Hewlett Packard" Nokia
do
echo "Manufacturer is:" $manufacturer
done

# The above can also be written as a single line...
for manufacturer in Apple Sony "Hewlett Packard" Nokia; do echo "Manufacturer is:" $manufacturer;done


# Rename a bunch of iPhone screenshot files from IMG_0001.PNG, IMG_0002.PNG...
# to ScreenShot01.png,ScreenShot01.png...

for name in IMG*PNG
do # Work out the new name
newname="$(echo $name | sed "s/IMG_00/ScreenShot/;s/PNG/png/")" # Move/rename the files
echo "renaming $name as $newname"
mv $name $newname
done

"In expanding the field of knowledge, we but increase the horizon of ignorance" ~ Henry Miller

Related:

break - Exit from a loop
while - Execute commands
continue - Resume the next iteration of a while or foreach loop


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