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introduction
shell
interface available on any UNIX-like OS
interesting: both UI and API
shell input [XCU 2.1]
specified file
'-c' option argument
stdin (interactive mode)
first steps: `echo` command [XCU 4]
ex. 1: Hello world
demonstration of input methods
ex. 1.1:
[sh]
$ echo Hello world
ex. 1.2:
[hello.sh]
echo Hello world
[sh]
$ sh hello.sh
ex. 1.3:
[sh]
$ sh -c 'echo Hello world'
magic number behavior, `chmod` [XCU 4], file modes
ex. 2: magic hello
[hello-magic.sh]
#! /bin/sh
echo Hello world
[sh]
$ chmod a+x
$ sh hello-magic.sh
field splitting [XCU 2.6.5]
simple commands: `cd`, `ls`, `mkdir`, `touch` [XCU 4]
ex. 3: field splitting
[sh]
$ mkdir foo bar
$ ls
tilde expansion [XCU 2.6.1]
ex. 4: tilde expansion
[sh]
$ ls ~
$ ls ~sh-foo
$ ls ~sh-foo/some-directory
pathname expansion [XCU 2.6.6] [XCU 2.13]
ex. 5: pathname expansion
[sh]
$ echo ~sh-foo/*-file
$ echo ~sh-foo/ba*/file
parameters: assignment
ex. 6: parameter assignment
[sh]
$ myparam=foo
$ mynum=1
parameters: expansion [XCU 2.6.2]
simple parameter
use default values
string length
remove {smallest,largest} suffix pattern
remove {smallest,largest} prefix pattern
ex. 7: parameter expansion
[sh]
$ echo ${myparam}
$ echo ${nullparam:-default}
$ echo ${#myparam}
$ file=main.c
$ echo ${file%.c}.o
$ dir=foo/bar/baz
$ echo ${dir##*/}
positional parameters [XCU 2.5.1]
ex. 8: positional parameters
[pos-params.sh]
#! /bin/sh
echo ${1}
echo ${2}
[sh]
$ chmod a+x pos-params.sh
$ sh pos-params.sh foo
$ ./pos-params.sh foo bar baz
special parameters [XCU 2.5.2]
@, *, #, ?, 0
exit status [XCU 2.8.2]
`false` and `true` commands [XCU 4]
ex. 9: special parameters
[spec-params.sh]
#! /bin/sh
echo Number of positional parameters: ${#}
echo Positional parameters: ${@}
echo Script name: ${0}
true
echo ${?}
false
echo ${?}
[sh]
$ chmod a+x spec-params.sh
./spec-params.sh foo bar baz
shell variables [XCU 2.5.3]
HOME, IFS, PATH, PS1, PWD
ex. 10: shell variables
[sh]
$ echo ${HOME}
$ echo ${PWD}
[sh (another shell)]
$ PS1='$ '
$ PS1='PROMPT> '
command substitution [XCU 2.6.3]
two versions
ex. 11: command substitution
[sh]
$ filepath=$(basename ~sh-foo/bar/file)
$ echo ${filepath}
arithmetic expansion [XCU 2.6.4]
ex. 12: arithmetic expansion
$ echo $((2+3))
$ echo $((0x10 + 4))
$ i=0
$ i=$(($x + 1))
$ echo ${i}
basic foundation complete
simple commands revisited [XCU 2.9.1]
simple-command: [parameter-assignment...] [word...]
command search and execution
pipelines [XCU 2.9.2]
lists [XCU 2.9.3]
AND-OR list
list
ex. 13: lists
[sh]
$ false && echo foo || echo bar
$ true || echo foo && echo bar
compound commands [XCU 2.9.4]
grouping
if, `test` command
while
until
for
case
functions [XCU 2.9.5]
I/O redirection [XCU 2.7]
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