Bash History Substitution
in [Shell]
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From: George on 1 Jun 2010 06:31 Dear All, I am a bit confused with the way bash history works. Say, for example, that I am running the following command: ls -l test1/ Now, if I do not remember the name of the previous directory I used but now I want to run an ls on the directory test2, I try running: !!:s/!!:1:p/test2 (to get the command echoed without executing) but I am getting the message that substitution failed. I know that I can use the up arrow to go back and simply substitute the name; what I am asking is why the history command does not work. I went through online tutorials and cheat sheets with event and word designators but can not see what I am doing wrong. Regards, George
From: Janis Papanagnou on 1 Jun 2010 12:12 George wrote: > Dear All, > > I am a bit confused with the way bash history works. Say, for example, > that I am running the following command: > > ls -l test1/ > > Now, if I do not remember the name of the previous directory I used but > now I want to run an ls on the directory test2, I try running: > > !!:s/!!:1:p/test2 (to get the command echoed without executing) (This is really aweful syntax, if you ask me.) If you don't mind another approach, use the history command fc; $ ls -l test1 $ fc -s 1=2 ls The second command will replace 1 by 2 in the _previous ls command_, or use just $ ls -l test1 $ fc -s 1=2 to replace 1 by 2 in the _previous command_. Janis > > but I am getting the message that substitution failed. > > I know that I can use the up arrow to go back and simply substitute the > name; what I am asking is why the history command does not work. I went > through online tutorials and cheat sheets with event and word > designators but can not see what I am doing wrong. > > Regards, > George
From: George on 1 Jun 2010 12:16 On 01/06/2010 17:12, Janis Papanagnou wrote: > George wrote: >> Dear All, >> >> I am a bit confused with the way bash history works. Say, for example, >> that I am running the following command: >> >> ls -l test1/ >> >> Now, if I do not remember the name of the previous directory I used but >> now I want to run an ls on the directory test2, I try running: >> >> !!:s/!!:1:p/test2 (to get the command echoed without executing) > > (This is really aweful syntax, if you ask me.) > > If you don't mind another approach, use the history command fc; > > $ ls -l test1 > $ fc -s 1=2 ls > > The second command will replace 1 by 2 in the _previous ls command_, > or use just > > $ ls -l test1 > $ fc -s 1=2 > > to replace 1 by 2 in the _previous command_. > > Janis > Thanks Janis for the prompt reply. I agree that the syntax is ugly, but I am just curious as to why it would not work. Also, the test1 and test2 directories are just examples - it could be bin and var or anything else. The idea is that you know you have run an ls -l command on a directory, you want to replace that directory name with a new one. I thought it will do it if I use the s designator for substitute and then !!:1 would be the first argument of the previous command. I just can't understand what is wrong there. >> >> but I am getting the message that substitution failed. >> >> I know that I can use the up arrow to go back and simply substitute the >> name; what I am asking is why the history command does not work. I went >> through online tutorials and cheat sheets with event and word >> designators but can not see what I am doing wrong. >> >> Regards, >> George
From: Janis Papanagnou on 1 Jun 2010 12:27 George wrote: > On 01/06/2010 17:12, Janis Papanagnou wrote: >> George wrote: >>> Dear All, >>> >>> I am a bit confused with the way bash history works. Say, for example, >>> that I am running the following command: >>> >>> ls -l test1/ >>> >>> Now, if I do not remember the name of the previous directory I used but >>> now I want to run an ls on the directory test2, I try running: >>> >>> !!:s/!!:1:p/test2 (to get the command echoed without executing) >> >> (This is really aweful syntax, if you ask me.) >> >> If you don't mind another approach, use the history command fc; >> >> $ ls -l test1 >> $ fc -s 1=2 ls >> >> The second command will replace 1 by 2 in the _previous ls command_, >> or use just >> >> $ ls -l test1 >> $ fc -s 1=2 >> >> to replace 1 by 2 in the _previous command_. >> >> Janis >> > > Thanks Janis for the prompt reply. I agree that the syntax is ugly, but > I am just curious as to why it would not work. Also, the test1 and test2 > directories are just examples - it could be bin and var or anything > else. The idea is that you know you have run an ls -l command on a > directory, you want to replace that directory name with a new one. You should be aware that you can do more complex substitutions with the fc command than just replacing 1 by 2. And also consider that, while your bash substitution is not only ugly but also non-standard, fc is a Unix standard (see http://www.opengroup.org/onlinepubs/007908775/xcu/fc.html). If you want someone to explain problems with bash specifics I really can't help you. Sorry. Janis > > I thought it will do it if I use the s designator for substitute and > then !!:1 would be the first argument of the previous command. > > I just can't understand what is wrong there. > >>> >>> but I am getting the message that substitution failed. >>> >>> I know that I can use the up arrow to go back and simply substitute the >>> name; what I am asking is why the history command does not work. I went >>> through online tutorials and cheat sheets with event and word >>> designators but can not see what I am doing wrong. >>> >>> Regards, >>> George >
From: Dave Gibson on 1 Jun 2010 13:27
George <me(a)me.com> wrote: > Dear All, > > I am a bit confused with the way bash history works. Say, for example, > that I am running the following command: > > ls -l test1/ > > Now, if I do not remember the name of the previous directory I used but > now I want to run an ls on the directory test2, I try running: > > !!:s/!!:1:p/test2 (to get the command echoed without executing) > > but I am getting the message that substitution failed. History expansions aren't nestable. Use the range word designator with a missing end-range ":0-" to select all but the last word: !!:0- test2 |