06-15-2017
Thanks for the friendly welcome Don. I haven't had any homework assignments for over 25 years. I'm a hobbyist working on a maths problem. I wrote a little C program to generate this data, and want to sort through it with shell tools as an intermediate step to solving the problem empirically (as a hint to myself, before I try to solve it mathematically). I am using Bash by default, since it is the default shell on my laptop running OS 10.6, but other shells are available. What I have done so far: stared at it and realised I don't know how to do this kind of multi-line search with the handful of shell commands I have taught myself over the last 30 years (and only used very infrequently, when such problems come up). I suppose I could also have tried to do this weeding out within my C program, but I can't see how to do it without having to hold everything in memory all at once (again, I write such programs very infrequently). So, it seems better to write it to a file then use some other tool in the shell to search that file. Hence my posting here. I'm sure there is a better way, but I break out my C and shell scripts about once every 6 months and at my age it's often easier to ask.
Is there anyone less suspicious who might be able to point me in a useful direction?
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chsh(1) General Commands Manual chsh(1)
NAME
chsh - change default login shell
SYNOPSIS
login-name [shell]
login-name [shell]
login-name [shell]
login-name [shell]
DESCRIPTION
The command changes the login-shell for a user's login name in the repository (see passwd(1)).
The DCE repository is only available if Integrated Login has been configured; see auth.adm(1M). If Integrated Login has been configured,
other considerations apply. A user with appropriate DCE privileges is capable of modifying a user's shell; this is not dependent upon
superuser privileges.
If the repository is not specified (as in [login-name]), the login shell is changed in the file only.
Run after running to make sure the information was processed correctly.
Notes
The command is a hard link to the command. When is executed, actually the command gets executed with appropriate arguments to change the
user login shell in the repository specified in command line. If no repository is specified, the login shell is changed in the file.
Arguments
login-name A login name of a user.
shell The absolute path name of a shell. If the file exists, the new login shell must be listed in that file. Otherwise, you
can specify one of the standard shells listed in the getusershell(3C) manual entry. If shell is omitted, it defaults to
the POSIX shell,
Options
The following option is recognized:
Specify the repository to which the operation is to be applied.
Supported repositories include and
Security Restrictions
You must have appropriate privileges to use the optional login-name argument to change another user's login shell.
NETWORKING FEATURES
NFS
File can be implemented as a Network Information Service (NIS) database.
EXAMPLES
To change the login shell for user to the default:
To change the login shell for user to the C shell:
To change the login shell for user to the Korn shell in the DCE registry:
WARNINGS
If two or more users try to write the file at the same time, a passwd locking mechanism was devised. If this locking fails after subse-
quent retrying, terminates.
AUTHOR
was developed by HP and the University of California, Berkeley.
FILES
SEE ALSO
chfn(1), csh(1), ksh(1), passwd(1), sh(1), sh-posix(1), getusershell(3C), pam(3), passwd(4), shells(4).
chsh(1)