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bash [2012/10/12 16:55] – [Bash Tips / Tricks] k2patelbash [2020/08/10 02:35] (current) – external edit 127.0.0.1
Line 121: Line 121:
 [ FILE1 -ef FILE2 ] True if FILE1 and FILE2 refer to the same device and inode numbers. [ 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. [ -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. [ -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. [ STRING1 == STRING2 ] True if the strings are equal. "=" may be used instead of "==" for strict POSIX compliance.
Line 271: Line 271:
 </code> </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 ==== ==== Control case ====
Line 357: Line 368:
 re='foo.*bar'; [[ $'foo\nbar' =~ $re ]] && echo 'yes' || echo 'no' re='foo.*bar'; [[ $'foo\nbar' =~ $re ]] && echo 'yes' || echo 'no'
 </code> </code>
 +
 +=== History Size ===
 +<code bash>
 +HISTSIZE=1500000
 +HISTFILESIZE=1500000
 +HISTTIMEFORMAT="[%Y-%m-%d - %H:%M:%S] - "
 +</code>
 +
 +=== Truth Table ===
 +<code bash>
 +These two commands not the same:
 +
 +command1 && command2 || command3
 +
 +if command1
 +then
 +command2
 +else
 +command3
 +fi
 +</code>
 +
 +In the if-then-else, exactly one of command2 or command3 will be executed. But in the && || version, command3 runs if either command1 or command2 returns false.
 +
 +<code bash>
 +for c1 in true false; do for c2 in true false; do echo "$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 ==== ==== Networked Info ====
  
bash.1350060950.txt.gz · Last modified: 2020/08/10 02:28 (external edit)