Differences

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--- bash [2011/10/18 13:11] – [Indirect Referance] k2patel
+++ bash [2020/08/10 02:35] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 ====== Bash ======
+  * [[ Floating Point Calculation ]]
 ==== Bash Short-Cut ====
@@ Line 119: / Line 121: @@
 [ FILE1 -ef FILE2 ]	True if FILE1 and FILE2 refer to the same device and inode numbers.
 [ -o OPTIONNAME ]	True if shell option "OPTIONNAME" is enabled.
-[ -z STRING ]	True of the length if "STRING" is zero.
+[ -z STRING ]	True if the length of "STRING" is zero.
 [ -n STRING ] or [ STRING ]	True if the length of "STRING" is non-zero.
 [ STRING1 == STRING2 ]	True if the strings are equal. "=" may be used instead of "==" for strict POSIX compliance.
@@ Line 269: / Line 271: @@
 </code>
+==== Bash alias and complition ====
+Using command completion for alias in bash.
+<code bash ~/.bash_profile>
+alias c='/usr/bin/ssh'
+export HLIST
+HLIST=`cat ~/.ssh/known_hosts | cut -f 1 -d ' ' | sed -e s/,.*//g | uniq | grep -v "\["`
+HLIST="${HLIST} $(cat ~/.ssh/config | grep Host | awk '{print $2}' | grep -v \*)"
+HLIST=$(echo ${HLIST} | sort | uniq)
+complete -W "${HLIST}" c
+</code>
+==== Control case ====
+In Bash 4:
+To lowercase
+<code bash>
+$ string="A FEW WORDS"
+$ echo ${string,}
+a FEW WORDS
+$ echo ${string,,}
+a few words
+$ echo ${string,,[AEIUO]}
+a FeW WoRDS
+$ string="A Few Words"
+$ declare -l string
+$ string=$string; echo $string
+a few words
+</code>
+To uppercase
+<code bash>
+$ string="a few words"
+$ echo ${string^}
+A few words
+$ echo ${string^^}
+A FEW WORDS
+$ echo ${string^^[aeiou]}
+A fEw wOrds
+$ string="A Few Words"
+$ declare -u string
+$ string=$string; echo $string
+A FEW WORDS
+</code>
+Toggle (undocumented)
+<code bash>
+$ string="A Few Words"
+$ echo ${string~~}
+a fEW wORDS
+$ string="A FEW WORDS"
+$ echo ${string~}
+a fEW wORDS
+$ string="a few words"
+$ echo ${string~}
+A Few Words
+</code>
+Capitalize (undocumented)
+<code bash>
+$ string="a few words"
+$ declare -c string
+$ string=$string
+$ echo $string
+A few words
+</code>
+Title case:
+<code bash>
+$ string="a few words"
+$ string=($string)
+$ string=${string[@]^}
+$ echo $string
+A Few Words
+$ declare -c string
+$ string=(a few words)
+$ echo ${string[@]}
+A Few Words
+</code>
+To turn off a declare attribute, use "+". For example, declare +c string. This affects subsequent assignments and not the current value.
+==== Bash Tips / Tricks ====
+=== Quating ===
+Bash has a special form of quoting, $'string' in which backslash-character combinations are expanded. For example, echo $'this is a literal tab: \t'
+<code bash>
+re='foo.*bar'; [[ $'foo\nbar' =~ $re ]] && echo 'yes' || echo 'no'
+</code>
+=== History Size ===
+<code bash>
+HISTSIZE=1500000
+HISTFILESIZE=1500000
+HISTTIMEFORMAT="[%Y-%m-%d - %H:%M:%S] - "
+</code>
+=== Truth Table ===
+<code bash>
+These two commands not the same:
+command1 && command2 || command3
+if command1
+then
+command2
+else
+command3
+fi
+</code>
+In the if-then-else, exactly one of command2 or command3 will be executed. But in the && || version, command3 runs if either command1 or command2 returns false.
+<code bash>
+for c1 in true false; do for c2 in true false; do echo "$c1 && $c2 || c3"; (echo c1; $c1) && (echo c2; $c2) || echo c3; done; done
+</code>
+And the output:
+<code bash>
+true && true || c3
+c1
+c2
+true && false || c3
+c1
+c2
+c3
+false && true || c3
+c1
+c3
+false && false || c3
+c1
+c3
+</code>
+[[ http://www.linkedin.com/groups/Tuesdays-tip-difference-between-if-3716796.S.236851680?view=&srchtype=discussedNews&gid=3716796&item=236851680&type=member&trk=eml-anet_dig-b_pd-ttl-cn&ut=0FCRGmx_LdW5I1 | Link to Article ]]
+==== Networked Info ====
+   * [[ Can we Hide Code ]]
 ==== Bash FAQ ====